I expect I've mentioned before that the research on homework at the elementary level is that it has negligible effects on academic achievement. (Over two hours a night and time on homework actually has an inverse relationship with achievement. Though that may be confounded by children with learning challenges.) Either you know it when you leave the instructional setting, and don't need the practice, or you don't know it, and don't benefit from practicing it incorrectly on your own. The data appear to support the primary value of homework (and even that is debatable) as one of work ethic.
Just as in the well-known aphorism:
"Work harder, not smarter!"
