I remember, in the first few years I was terribly studious and hard-working, I've done as much homework as I could, I've got the best grades possible, always scoring higher than 90%. As I grew older, I've started to notice what an utter crap our educational system is: highly unqualified teachers, boredom and stress in 35 hours a week. I refused to do my homework, and learned some really interesting stuff instead. Results: I still scored higher than my peers, and I had a lot of free time with less stress.
So yeah, homework doesn't help at all ~ but this is far from the biggest problems concerning education imo.