I have two thoughts about falling asleep, and I realize that falling asleep happens differently for different people.
The first idea has already been mentioned and that is to start reading in bed. Since you are in school, I would suggest reading your school books. One of two things will happen... Either you will fall asleep, or if you don't, you will be one of the best read students in school and should be able to ace all of your tests. You might actually get out of school having learned something.
I though of the second idea after seeing something at a friends house. They recently had a pretty cool (i'm dating myself) mural painted on their ceiling. It is a mural that is invisible in light and is painted with glow in the dark paint. It is a mural of the night sky and they lie in bed and look up into a real looking night sky as they fall asleep. They say that it is great. I am going to have one painted for my daughter who has a hard time falling asleep too, and one for myself. I would check out their site and maybe see if they have someone in your area who you could call. If they don't have someone there, they might be able to find someone for you.
if neither one of those suggestions works for you, then I don't know what to suggest. I never go to bed early, but if I did I would fall asleep pretty fast with a book, even a good one.
Good luck!