Check out the National PTA and the National Education Association guidelines," University of Missouri psychology professor Harris Cooper, author of a pioneer study on the effect of homework on student achievement, told Education World. "For children in grades K through 2, homework is most effective when it does not exceed ten to 20 minutes each day. Children in grades three through six can handle 30 to 60 minutes a day. If educators and parents expect homework far out of line with these recommendations to result in big gains in test scores, they are likely to be disappointed.