Heh. I was one of those kids you couldn't pin down to do homework, no matter what you did. And, oddly, I graduated 6th in my class with an A average. Never failed anything important, either.
Homework is supposed to be there to help kids get more clarity. Unfortunately, there usually IS a ridiculous amount of homework to be done, and, depending on what the kid wants to do with his life, a college degree may not be needed.
For instance: Photography. A degree is nice, but working with an experienced photograper is better.
Cartoonists: again, nice if you have one, but experience trumps it.
Hell, vet techs don't get degrees, they get certifications. Sometimes. I.E.: I am a tech, but have no license. I am getting on the job training, and have the same level of experience with small animals as many licensed techs do. All my training has been directly from a doctor, so.
Yah. It depends.
Really, your best bet is to stop nagging the kids. It's not going to make 'em do their homework. Trust me. And you might want to find out if they even /care/ about going to college. Some kids don't, and never will. And NEVER try to force them to change their minds, or go against their better judgement. It'll be a disaster.