I had a problem with the homework that my kids brought home when they were attending Town Creek Elementary. My problem wasn't with the amount, it was with the source.
When I was in school, the teachers assigned homework assignments out of the text books we were using. That way if I had questions, or needed help, I could look up the information in the book. While at TCE my kids kept bringing home these assignments that had been copied out of unknown sources, and if they needed help I often couldn't help them because the references listed on the assignement sheet weren't available or weren't listed on the assignment sheet.
When I complaigned to my daughter's teacher I was told that most of the assignments were coming from a text book that was meant for kids in fifth grade... except my daughter was in the second grade. He felt that the kids were able to handle the advanced work, and I told him that if these kids were supposed to be learning fifth-grade level materials, the second-grade materials would be written at the fifth-grade level.
If your student is bringing home materials that are beyond their capabilities (like the assignment has complicated written instructions for a student who can't read yet) the teacher is deviating from the training plan. You may feel good that with your help your student can get the assignment done, but the fact is that your student isn't using that time to learn the things that they are supposed to be learning.