Tanzania, Sept. 3 -- Dar es Salaam. For many pupils and students preparing for national examinations, school has become an almost full-day commitment, with some private schools keeping learners in class from as early as 6am until late in the evening.

In some schools, pupils and students attend regular lessons until around 3pm before returning for evening tuition or private lessons from about 4pm to 9:30pm.

While schools and parents argue that the additional hours help improve academic performance, the demanding schedules have raised questions about how much studying is too much and the health and developmental effects of leaving children with little time to rest.

Education is essential, but children also need adequate sleep, physical a...