Is spending more hours in class better for learning?

Regardless of the type of school attended (public or private, advantaged or disadvantaged), 15-year-old students spent more time in mathematics lessons in 2012 than in 2003. The average amount of time spent in mathematics classes varies by more than a factor of two across countries and economies. The more time spent in mathematics classes, the better students perform, on average; but giving students more work in class is often not enough to improve learning outcomes.