Time in the class and educational attainment: evidence from PISA

In the soul searching that has followed the release of the Leaving & Junior Certificate exams and particularly in the context of the maths results some commentators have pointed to the relatively low hours in class spent by Irish students. Does it actually matter? This paper shows that it does:

Do Differences in School's Instruction Time Explain International Achievement Gaps in Maths, Science and Language? Evidence from Developed and Developing Countries
Victor Lavy
There are large differences across countries in instructional time in schooling institutions. Can these differences explain some of the differences across countries in pupils' achievements in different subjects? What is the likely impact of changes in instructional time? While research in recent years provides convincing evidence about the effect of several inputs in the education production function, there is limited evidence on the effect of classroom instructional time. Such evidence is of policy relevance in many countries, and it became very concrete recently as President Barrack Obama announced the goal of extending the school week and year as a central objective in his proposed education reform for the US. In this paper, I estimate the effects of instructional time on students' academic achievement in math, science and language. I estimate linear and non-linear instructional time effects controlling for unobserved heterogeneity of both pupils and schools. The evidence from a sample of 15 year olds from over fifty countries that participated in PISA 2006 consistently shows that instructional time has a positive and significant effect on test scores. The effect is large relative to the standard deviation of the within pupil test score distribution. The OLS results are highly biased upward but the within student estimates are very similar across groups of developed and middle-income countries. However, the estimated effect of instructional time in the sample of developing countries is much lower than the effect size in the developed countries. Several checks for threats of identification support the causal interpretation of this evidence. I obtain very similar results when I use as an alternative data from primary and middle schools in Israel and a somewhat different identification strategy