Homework should be banned because there is no evidence that it correlates to better learning or grades. Additionally, too much homework can detract from other important activities and relationships that are essential for the child's development.
Though having been a staple of school for generations, there is actually little if any evidence to suggest homework has any real benefit for children. The supposed goal of it is to reinforce concepts taught during the school day, but studies suggest that the benefits of homework are negligible at best. There is no statistical relationship between homework and how well a child does in school, especially in elementary school.
Additionally, there are detriments to children being assigned too much homework, detriments that some argue would negate any benefits, however small, that homework might bring. For example, homework detracts from family time. It also makes it difficult for children to engage in free play and to strengthen bonds with neighbors and friends. Balancing a heavy homework load with extracurricular activities can be all but impossible, which can result in children engaging less often in other worthy pursuits, such as learning a musical instrument or participating in sports.
Some studies do suggest that if homework is to remain, educators must take a good hard look at quality over quantity to ensure that the types of assignments they give actually have value rather than being assigned for the sake of tradition or routine.