Seventy minutes of homework a day doesn't seem like a lot but a Spanish study suggests that it might be the perfect amount of time to improve grades, particularly in math and science.

Researchers analyzed the performance of about 7,700 boys and girls with a mean age of about 13.  A couple of things were discovered right off the bat.  Kids did better in standardized tests when assigned homework and when they did it without any assistance.

However, the time spent doing homework was crucial when it came to math and science scores, which declined a bit when students were given between 90 and 100 minutes of homework.

Furthermore, the improvement in scores when 70 to 90 minutes of homework was assigned was negligible. Therefore, 70 minutes of homework is preferable.