Do this and then you'll have your top performers start being absent as well -- out of boredom.
I'd suggest sending kids that are lagging behind, and those that have high absentee rates, into remedial classes. Education should get kids excited about learning. From my experience, nothing gets kids more excited than the feeling that they've accomplished something. Make them sit in a room to rehash the same old crap over and over and you lose the ones you want.