I'm reading "How Children Fail", by John Holt. I like this passage:
We say and believe that at this school we teach children to understand the meaning of what they do in math. How? By giving them (and requiring them to give back to us) "explanations" of what they do. But let's take a child's-eye view. Might not a child feel, as Walter obviously did, that in this school you not only have to get the right answer, but you also have to have the right explanation to go with it; the right answer, and the right chatter. Yet we see here that a "successful" student can give the answer and the chatter without understanding at all what he is doing or saying.
P.S. "How Children Fail" is an in-depth description of John Holt's experiences teaching in an elementary school. I've read a lot of the book, and I haven't seen homework mentioned once. The book is copyright 1964.