Did you see this article in the New York times about homework?
If not, make sure you read it and start applying what it says. For homework to be effective it must not be long or short but smart. The author offers 4 ways to make homework smarter:
1. Space Repetition;
2. Retrieval Practice;
3. Cognitive Disfluency;
4. Interleaving.
Read the article, try the techniques and improve student learning!!