Hi J.---I agreee with others that parental involvement is the key. You may need to address the kids apathy from that angle. I'd bet that will be even harder, but without the parents expectations for their children's success, I'm afraid that most of the kids will only work hard enough to get by.
When addressing the issue of grades, my husband told our kids that good grades insured options. If a student aspires to being a ditch digger, he or she can do so, even with a straight A average. But if that student suddenly decided he wants to be a professional, a doctor, lawyer, any career goal that requires good grades, then the student is set up for success.
We expected our children to do well. Our older two were given a little more lattitude, and while they are successful people, we could have, and should have required more of them through high school. Our youngest, who just graduated HS, is starting at MSU with 19 credits because we insisted on AP classes, something we didn't do with our older two. We have been much more involved with his school 'career', and plan to do so all through college.
Another idea might be to address the social needs of kids this age. They are usually so busy with activities after school, that socialization is very difficult. And there are very few parks or other activities for teens outside of school. Any time there is a gathering of them, the police will get involved because they suspect the worst. If a time for their social needs could be addressed within the school setting for a short time, maybe then they would be able to 'focus' better on their academics.
I hope this is of some value. But unfortunately, the most effective solution to this problem requires parental involvement, and how to reach them is the million dollar question. Good luck. D.