My daughter is only 2, so I'm not sure how I feel about it in primary school. But I fully support a reasonable amount of it in high school. For example, in Maths, we would learn a concept, work through an example question as a class, then be told to complete these 20 questions to practice the concept. We would start this there with the teachers help available, then finish it for homework. It reinforced what we learnt in class. If we didn't have homework, it would take way longer to get through concepts and I think a lot would be forgotten from one lesson to the next.