I would say to change your goal.
Instead of changing yourself to get into a top school, changes the schools you are looking at to fit you.
You see yourself as someone who could be an A student but are really doing the actions of a C student.
Start this very day into being an A student. here are ideas:
http://talk.collegeconfidential.com/high-school-life/2026961-what-to-do-when-you-arent-doing-well-in-a-hs-class-p1.html
Decide that you are going to learn good habits in studying.
So lets say you decide then to go to Community College, then get A’s, and then transfer to your State U and do well.
Or you can go to a less selective college and really shine and get involved with professors and do research and go on to gradschool.
Don’t think of not getting into a very selective school as a failure…the only failure you will have is not changing what you are doing for fear of failure.
Also keep in mind that colleges like to see an upward trend in grades…it means that you are doing better in harder classes.
Spend this summer studying for the ACT/SATs as that will help your case.