Does class time imply better academic achievement?

Spain presents a high amount of instruction time in comparison to other countries; however the results of international large-scale assessments seem to indicate that it is not among the best academic performer countries. Because of that, the current research intends to shed some light in this issue for the case of Spanish students aged 15. Our approach is twofold: first, we intend to study the potential relationship between instruction time and students’ academic achievement; second, we evaluate the extent to which this potential link present heterogeneity among Spanish regions, due to their capacity to set their own amount of instruction time. In order to accomplish this aim, PISA 2009 and 2012 data has been employed. The use of students’ fixed effects in this research has let us to isolate the effect of instruction time on students’ academic achievement from other covariates. Our main results have shown that students’ academic achievement does not seem to be affected by the amount of instruction time and that this lack of effect happens in all the Spanish Autonomous Communities. Many robustness checks have corroborated these results.