CLASSROOM HOURS: International evidence of the impact on student achievement

The longer the time that teenagers spend in the classroom, the better their results. That is the central finding of research by Professor Victor Lavy, published in the November 2015 issue of the Economic Journal. Analysing data on instructional time and school students'' achievement in over 50 countries, his study finds that longer classroom hours have a significant positive effect on test scores, particularly in developed and middle-income countries.

The evidence also suggests that the productivity of instructional time is higher in countries that have implemented school accountability measures or that have given schools autonomy in budgetary decisions and in hiring and firing teachers. Overall, the effects of additional classroom hours are large compared with the evidence for other school-level interventions intended to improve results.

The amount of time that students spend in schools varies widely from one country to another. For example, among European countries such as Belgium, France and Greece, 15-year-old students receive an average of more than 1,000 hours per year of total compulsory classroom instruction; while in England, Luxembourg and Sweden, the average is only 750 hours per year.

There are similar cross-country differences in the number of classroom lessons per week in different subjects. These are evident in data from the 2006 Program for International Student Assessment (PISA), a unique international education survey of 15-year-old students conducted by the Organization for Economic Co-operation and Development (OECD) and designed to allow for cross-country comparisons.

For example, these data show that 15-year-old students in Denmark receive four hours of instruction per week in mathematics and 4.7 hours in language, while students of the same age in Austria receive only 2.7 hours of weekly classroom lessons in mathematics and 2.4 hours in language. Overall, total weekly hours of instruction in mathematics, language and science is 55% higher in Denmark (11.5 hours) than in Austria (7.4 hours). Similar magnitudes of disparities in instructional time appear among the East European and developing countries that are included in the PISA 2006.

The new study analyses PISA 2006 data to investigate whether these large differences in instructional time explain some of the differences across countries in students'' achievements in different subjects. The results show that instructional time does indeed have a positive and significant effect on the academic achievements of students.

The effect of instructional time is larger for girls, immigrants and students from families of low socio-economic status. In addition, while estimates based on the sample of the formerly communist East European countries are very similar to the average effect obtained from the sample of OECD developed countries, the evidence based on a sample of developing countries suggests a much lower effect of additional instructional time on test scores.

The evidence also suggests that the productivity of instructional time is higher in schools that operate under well-defined accountability measures. Longer classroom hours also have a bigger impact in schools that enjoy extensive autonomy in budgetary decisions and in hiring and firing teachers. These findings emphasise the importance of quality and quantity of instructional time in bridging the gaps in student achievement across countries.


The author comments:

''From a policy perspective, any evaluation of the merits of adding instructional time should take into account its cost relative to other potentially beneficial inputs or interventions.''

''Policy-makers would be advised to consider that adding instructional time in a given subject may be associated with beneficial spillover effects by leading to more demanding and advanced coursework.''

''For example, if students from one school or country spend twice as much class time on mathematics than students from another school or country, they are much more likely to cover algebra rather than just geometry.''

''Such an increase in the level of challenge in coursework may lead to improved performance in PISA along with the effect realised solely through more time devoted to subjects.''


''Do Differences in Schools'' Instruction Time Explain International Achievement Gaps? Evidence from Developed and Developing Countries'' by Victor Lavy is published in the November 2015 issue of the Economic Journal. Victor Lavy is at the University of Warwick and Hebrew University of Jerusalem.

Victor Lavy

professor of economics at University of Warwick and the Hebrew University of Jerusalem