Instruction time and educational outcomes

The quality of instruction and the activities it replaces determine the success of increased instruction time

Universidad de los Andes and Centre for Economics Performance (LSE), Chile

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Elevator pitch

Increasing instruction time might seem a simple way to improve students' outcomes. However, there is substantial variation in its effects reported in the literature. When focusing on school day extensions, some studies find no effects, while others find that an additional hour of daily instruction significantly improves test scores. A similar pattern arises when examining the effect of additional days of class. These mixed findings likely reflect differences in the quality of instruction or in the activities that are being replaced by additional instruction. Hence these elements need to be considered when designing policies that increase instruction time.

Allocation of manadatory instruction time in primary education

Key findings


Increasing instruction time can significantly improve students' performance.

Using additional time to reinforce content seems to help reduce inequality on test scores.

Reducing absences is an effective way of increasing instruction time and improving students' performance.

Returns to instruction time are greater in schools that offer a better learning environment, and in those that have greater autonomy.

Instruction time extensions can reduce teenage pregnancy and youth crime.


Increasing instruction time does not necessarily generate large gains in students' performance.

It can be expensive to increase instruction time.

Implementing instruction time changes can be difficult and some schools might struggle to adapt.

Using additional time to cover new content seems to be more beneficial for high-performing students, increasing both within and between school inequality.

Extending instruction time too much could be detrimental.

Author's main message

Instruction time extensions are not trivial. To make them effective, policymakers should consider how other elements of the school system-such as school infrastructure, school resources, and teachers-will be affected. These elements, as well as the type of activities that will be replaced by the additional instruction should be considered when designing such policies. In addition, deciding whether to use the additional time to reinforce or introduce new topics is important as it impacts which students will benefit the most.

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