B.H.
As a parent of 4 mostly grown kids, I was never successful in "pushing" my kids to put more effort into schoolwork. I think I should have been more structured about homework time. But as a consolation (and maybe there's some advice hidden in here) studies have shown that the more kids feel like they are doing the work and learning as their choice, the more they actually remember after the test is over and the more they are self-motivated. Punishments and rewards both convey the same message--there's no reason you would want to do this if you weren't forced/bribed. Structure (i.e. dinner/games/TV or whatever only comes after homework is done) and showing real interest in the content of what is learned may help. Good luck!!!
The Psychology of Parental Control:How well-meaning parenting can backfire by Wendy Grolnick is a good source for quality information.