The research literature on the relationship of time to learning spans the course of at least three decades, most of it falling into the following categories:
While much of the theoretical and anecdotal literature is compelling, in order to provide policy makers with a solid basis on which to evaluate the efficacy of extending education time, this review focuses primarily on the empirical evidence about the relationship between time and achievement.
Limitations of Existing Research
Despite the considerable number of research studies and reviews of research, the body of empirical literature is limited in some respects. While many studies have examined the relationship between school time and student learning, most have relied heavily on correlational data. There has yet to be a controlled study, employing an experimental design, that directly measures the impact of significantly extending the school year on student achievement outcomes. (6) Without this, estimates of how great an impact a given increase in time would have remain somewhat speculative. In addition, there have not been any longitudinal studies of the impact of increasing education time on student achievement. This has led one researcher to speculate that, while increasing education time appears to lead to only modest achievement gains in the short run, the cumulative impact of increased time might be considerable. (7)
Defining the Terms
Any examination of the research on the relationship between time and learning is complicated by the variety of ways in which researchers talk about time. While some studies define it somewhat generically, (e.g., "the school day"), others make distinctions between different subsets of time depending on how it is used by schools, teachers and students. If one is to compare findings among studies, understanding the definitional distinctions is critical.
Education time as researchers view it is perhaps best understood as a vertical continuum of sorts. Picture an inverted pyramid. At the top is time most broadly described, most easily measured, most abundant and most easily mandated: the number of hours in a school day and days in a school year. At the bottom is time most narrowly focused, most difficult to measure, most elusive and most difficult for policy makers to influence: those moments when learning is actually taking place.
Allocated time. At the top of the continuum is the most generic type of education time, allocated time, which refers to the total number of days or hours students are required to attend school. Moving down the continuum, allocated time can then be broken into instructional time and non-instructional time. The former is time spent in class, whether for core academic subjects like math, science and language arts or for non-academic electives, such as driver's education. Non-instructional time, by contrast, is that portion of the day devoted to lunch and recess, to passing between classes, to school assemblies and to other non-classroom activities.
Engaged time. Next on the continuum — a subset of instructional time — is engaged time, during which students are participating in learning activities. While any 50-minute class period (so called instructional time) may nominally be devoted to a particular subject, such as history, in reality, some portion of the period is almost always consumed by activities having little or nothing to do with learning, such as roll call, disciplinary issues and interruptions by announcements coming over the public address system. Thus, in trying to understand the relationship of time to learning, researchers narrow their focus yet again, this time honing in on that portion of the period when students are both in class and participating in instructional activities. Engaged time is also referred to in the literature as "time-on-task."
Academic learning time. Finally, at the bottom of the continuum is that time when learning actually occurs. Simply because a student is engaged in instructional activities does not necessarily mean he or she is learning. For example, an advanced student who is asked to spend 30 minutes going over material he has already fully mastered, will not be learning because there is nothing for him to learn. Similarly, a student who is involved in an instructional activity that covers advanced material for which she is not yet prepared is also unlikely to learn. With this in mind, researchers have focused in on academic learning time as that precise period when an instructional activity is perfectly aligned with a student's readiness and learning occurs.
The Basic Findings
The majority of studies dealing with the relationship of education time to student achievement look at allocated time, while other studies focus on engaged time or academic learning time. In some cases, the time variable being studied is not clearly specified. This inconsistency can make it difficult or misleading to compare studies. It also helps explain why, looking at the entire body of research on time and learning, there appear to be mixed findings about the degree to which time influences student learning.(8) However, despite this variability, the literature reveals a fairly consistent pattern:
In short, time does matter. How much or little it matters, however, depends greatly on the degree to which it is devoted to appropriate instruction. Remembering the inverted pyramid, any addition to allocated education time will only improve achievement to the extent it is used for instructional time, which must then be used for engaged time, which, in turn, must be used effectively enough to create academic learning time.
Focusing in on the Time that Matters
By and large, most researchers and policy makers interested in the relationship of time to learning have focused on allocated time. Researchers' propensity to look primarily or exclusively at the total amount of school time persists, in part, because quantity is easier to identify and measure than is quality; (10) measuring engaged time and academic learning time, by comparison, requires systematic and, to some extent, subjective judgments about how time is used. Allocated time is also the crudest and least helpful measure in trying to assess how time relates to learning precisely because it fails to consider how schools, teachers and students are using time and the quality of instructional activities.
A review of the research literature on how time is divided up during the school day shows that a large portion of potential learning time is typically eaten up by non-instructional activities, which have little relationship to student learning. (11) This leaves a relatively small portion of the school day for instructional time, in general. By extension, even less time remains, then, for instructional time in academic subjects -- time that is essential to student achievement. (12)
Within the classroom, potential learning time is often further eroded by such factors as inefficient classroom management, disciplinary activities, ineffective instructional techniques, inappropriate curriculum and student inattention or absence. Based on such factors, classrooms vary greatly with respect to the proportion of time that could be considered engaged time. But, in most cases, at the end of the school day -- or year -- the amount of engaged time ends up having been but a small subset of the overall time originally allocated for learning. For example, one study found that students were engaged in learning activities only 28 to 56 percent of the total time spent in school in a given year. (13) Another calculated that only 38 percent of a typical school day was devoted to "engaged time" in the schools it studied. (14) Studies have shown that the proportion of allocated school time in which students are engaged in learning activities varies by state, by district and by classroom. (15)
Research studies show no consistent relationship between the amount of time allocated for instruction and the amount of time students spend engaged in learning activities. (16) In other words, the length of a particular school day or year says nothing about how much time is devoted to learning activities. This means that increasing the amount of allocated time would not produce a predictable increase in students' engaged time. (17) In fact, increasing the length of the school day or year might not lead to any increase at all in the amount of time students are engaged in learning. Therefore, policies aimed at increasing the length of the school year could potentially have little impact on student learning.
Taking into account both the variability of allocated time to engaged time and researchers' tendency to focus on allocated time, it's little surprise that research findings about the degree to which allocated time influences learning are mixed: some studies find no consistent relationship between allocated time and student achievement and others find a small positive relationship. (18) But most studies conclude that allocated time, while necessary for producing learning outcomes, by itself doesn't suffice.
The Costs of Adding Time
Despite the fact that increasing allocated time offers no guarantee of improved student learning, policy makers are still drawn to increasing time as a lever for reform. As evidenced by Oregon's experience, however, the costs alone can be daunting. In fact, the high cost of extending allocated time has been a primary reason that more states and districts have not substantially increased the length of their school day or year. (19)
Cost estimates for increasing allocated time in school vary widely. According to one estimate, lengthening the school year would cost states between $2.3 and $121.4 million for each additional day, depending on the state, or an estimated $1.1 billion nationally. (20) It would cost the state of California approximately $50 million annually for each district to add a single instructional day, according to another recent estimate. (21) What's more, increasing allocated time to the extent called for in A Nation at Risk -- from about 180 days to 210 or more days -- would by most estimates cost in the tens of billions of dollars nationally.(22) One relatively recent estimate, prepared for the National Education Commission on Time and Learning, predicted that increasing the school year nationally to 200 days would cost between $34.4 and $41.9 billion annually. (23)
Pointing to the small achievement gains that could be expected from adding even substantial amounts of time to the school calendar, many researchers have concluded that the cost could not be justified, and that other education reforms would likely provide more impact. (24) Unfortunately, there has been little comparative research on the cost effectiveness of various school reform efforts. One study, by the Institute for Research on Educational Finance and Governance, examined the relative merits of four variables -- time, peer tutoring, class size reduction and computer-assisted instruction. It found that increasing time was the least cost-effective of the four interventions in terms of math performance and the next to least effective for reading performance. (25)
Maximizing Existing Time: Key Factors
Given the weak link between allocated time and student learning, and given the expense of adding time, how should we begin rethinking education time? The body of research evidence suggests that before simply adding more of it, schools and districts should, instead, make better use of existing time. (26) And since the majority of studies find that increasing students' time-on-task leads, at best, to modest increases in achievement, (27) schools must, minimally, find ways to increase the proportion of time students are involved in instructional activities. (28) From a school site policy perspective, this means ensuring, first, that adequate allocated time is devoted to instruction in those core academic subjects in which we seek improved student performance. Further, school administrators must find ways to minimize activities that reduce the potential for engaged time in any class, such as the public address system announcements that can greatly interrupt learning time.
But even creating more engaged time, as important as it is, does nothing to advance achievement unless the instructional activities lead to real learning. Here the quality of teaching is key. One research review reveals that when coupled with good teaching methods -- particularly, timely and specific feedback, attention to what a student already knows and the active participation of the teacher -- time has a significant impact on achievement. (29) Another review concludes that the "combination of additional time with effective teaching strategies and curricula designed to engage students is a powerful tool for enhancing academic performance." (30) In this instance, engaging students means choosing the instructional strategies and curriculum that will enhance a student's motivation to learn.
Tailoring engaged time to the needs of individual students is essential if all students are to learn more. The research suggests that the higher the quality of instruction, especially as it accommodates students' differing education backgrounds, abilities and learning styles, the greater the academic achievement. (31)
Thus, as many studies point out, unless you can somehow ensure that any added school time would be devoted to instruction, with students engaged in well-designed and appropriate learning activities, providing more time per se cannot be expected to have a major affect on student achievement. (32)
So what factors help ensure that classroom time becomes true learning time? The research literature points to three key quality factors that, in conjunction with time, contribute to improved student learning. Two of them -- classroom management and appropriateness of instruction -- fall largely to teachers. The third -- student motivation -- lies partly in the lap of the student, partly in the lap of his or her teachers and partly in the lap of the broader community.
Classroom management. Site level policy makers could reschedule the school day to include more instructional time, but how teachers use that time once the classroom door closes is difficult to regulate. As described earlier, research has documented great variation in the amount of allocated time devoted to instructional activities. Of course, some non-learning activities that occur in the classroom are beyond the control of any teacher, such as interruptions by p.a. announcements, fire drills, or the need to take roll, for example. However, studies show that much of the variation is due to teachers' behaviors, including their relative skills in classroom management. Several studies found that poor classroom management resulted in teacher and students losing considerable amounts of instructional time to student disruptions, waiting, long breaks between activities, student tardiness and various management and discipline activities. (33) One of the studies found that more than half of elementary school class time was occupied by non-learning activities, such as waiting, general management activities and other non-instructional activities. (34) By one estimate, 70 percent of teachers need to improve their classroom management skills. (35) According to one research review, even though research is inconclusive about the most effective and practical ways to increase time, most researchers concur that improving teachers’ time management techniques would be a good place to start. (36)
Appropriateness of Instruction and Curriculum. There is consistent research evidence that, in order to enhance student learning, instruction must be provided at a level of difficulty appropriate to the individual student. In other words, the subject matter provided must be matched to the readiness of students to learn it. When this is the case, time matters most. Based on a review of the research literature, one report concluded that the amount of time students spend engaged in learning activities that are appropriately challenging has a powerful and consistent effect on the amount of learning that occurs. (37) Various studies have shown that appropriate instruction consists of learning activities that are geared to the learners' abilities and background, such that students are both challenged and able to experience success. As noted earlier, instructional practices that promote student achievement include timely and specific feedback, attention to prior learning and active participation of the teacher. (38)
It is also critical that instructional practices be geared to student learning differences, including differences in how quickly students learn and how much time they require to learn. (39) Research has demonstrated that it is a waste of time to have students repeatedly go over materials they have already mastered and, equally so, to present materials to students that they are not prepared to learn. (40) In fact, as several researchers warn, such practices can be detrimental to students, reducing their motivation to apply themselves to academic learning and leading, eventually, to frequent absences or even to dropping out of school all together. (41)
For teachers to plan and deliver appropriate instruction requires that they have the ability to see the content -- whether mathematics, science or anything else -- through the eyes of their students and to know what instructional experiences and subject matter can be used to capitalize on a student's thinking. If they are to do so, teachers must start with a deep understanding of the content they teach. The advent of standards-based education makes this all the more essential: if student achievement is to rise to the high standards being set for what we expect students to know and be able to do, the curriculum must reflect the higher standards and teachers must be able to teach to the higher standards.
Student Motivation. Students themselves play an important role in determining the extent to which the time they spend in school will be truly educational. If existing or additional time is to be put to good use, students must be motivated to learn. As one researcher suggests, students make their own decisions about how they will allocate their time and effort to learning tasks, (42) and students who are highly motivated to learn will do so. According to one study, when students are highly interested in a learning activity, they will learn more in a given period of time than when they are less engaged. (43) In addition, increasing student motivation has been demonstrated to lead to better student attendance, thus increasing the amount of time students spend in school, (44) and, therefore, their potential to benefit from appropriate instruction.
Motivation may derive extrinsically from rewards (or punishments) such as grades, promotion, jobs and opportunities. Traditionally, schools, communities, teachers and parents have relied heavily on such extrinsic rewards to motivate students to apply themselves to learning tasks. But, some researchers have suggested that traditional extrinsic rewards may be less of a motivation for students than they once were. (45) After all, for example, graduating from high school, in and of itself, no longer ensures students of being able to go on to college or to get a good job.
Motivation can also be intrinsic, with a student finding the process of education rewarding in itself. A teacher can seed motivation by involving students in exciting, challenging and relevant instructional activities. Conversely, a teacher may squelch a student's motivation through poor instructional practices, such as repetitive seat work, lessons that lack real-world relevance for students and frequent testing.
There is some research evidence that intrinsic motivation may be more powerful than extrinsic motivation when it comes to academic performance. For example, several studies have shown that students are motivated by working in cooperative groups or teams, rather than competing as individuals, and that teamwork increases both achievement and motivation. (46) Another study demonstrated that regardless of how well they perform, students were more motivated by the idea of improving their personal performance than by performing better than their classmates. (47)
So if Time isn't the Issue, Why are We Behind?
As mentioned earlier, one reason policy makers and the general public are drawn to the idea of an extended school year is the perception that some of our international counterparts outperform us because they spend more time in school. As with the relationship between time and student performance, the explanation for why U.S. students lag behind their international counterparts appears to be more complex than merely a difference in how much time they spend in school.
At the middle school level, findings from the Third International Mathematics and Science Study (TIMSS) reveals no clear pattern in the relationship between the number of in-class hours teachers reported spending on instruction in math and science and student performance in those subjects. (48) The same is true at the fourth grade level: in four of the seven nations that outperform the U.S. in mathematics, students spend less time in class per week than do U.S. students and also less than the international average. (49) The TIMSS research also suggests that instead of adding time, greater attention should be paid to curriculum, specifically, to the depth and breadth of subject matter covered. (50)
Another study -- a review of the literature comparing U.S. and Asian education systems -- found, as did the TIMSS study, that factors other than time appeared to account for differences in student performance. (51) This study, like much of the research already cited, concluded that it was not the quantity of time that mattered, but how the time was spent. It found that what seems to account most for differences in achievement are factors such as the quality of teaching and curriculum and the role of parents. There also appear to be important cultural differences with respect to the value placed on education. Specifically, many Asian cultures place a higher priority on education. Academic learning is considered a primary responsibility for students, who consequently spend less time playing sports, working, doing household chores and engaging in leisure activities, such as watching television. Instead, Japan, for example, students spend large amounts of time outside of school doing homework and receiving tutoring, which increases the amount of learning time.
This paper was prepared for the PACE Media/ Education Writers Seminar (April 20, 1998).
Funding for this paper is partially provided by the U.S. Department of Education, Office of Educational Research and Improvement. The contents of this document do not necessarily reflect the views or policies of the U.S. Department of Education.
For more information, contact Joy Zimmerman at:
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