I have to disagree with #4, at least as it's stated. Maybe you are talking about a very good private school or a self-paced Montessori program, but in normal public schools the teacher doesn't slow down or speed up the material for individual children. If that were true, then your point would be invalid anyway since as soon as it was clear that the foundational material was giving the child problems, the teacher would slow down and correct that. Obviously that doesn't happen.

Correcting your child's homework is the *only* way to ensure that your child builds a good store of foundational knowledge in the subject. If your child misses a question, the teacher is not going to sit down privately with him and explain what was wrong and how to fix it! But you, as the parent, have that leisure.

Another thing the teacher won't correct is sloppy work (bad handwriting, miscopying numbers, accidentally skipping problems). The teacher just marks it wrong -- a math teacher, for instance, obviously doesn't have time to teach handwriting skills to individual children. Don't underestimate the impact that these seemingly minor problems have on your child's self esteem and enjoyment of the subject.