Homework.

Those assignments, questions, problems, projects, papers that teachers give to students to complete outside of regular classroom time.

It seems to be part and parcel of the formal schooling experience. Students have homework. That's just the way school "works." 

Yet, in spite of its seeming simplicity and central place within education, homework is quite a controversial issue. It has strong proponents and fierce opponents among administrators, teachers, parents, and students at all levels of education.