Don't come straight home after school. Instead, plan on going to somewhere like the library for an hour and a half. Make up your mind that, during that time, you will tackle some school work. You'll be free of distractions in a place like the library.

This worked great for me one summer that I had to take a hard course. I went from class to lunch and, then, to the library. I became my routine and I got to like it.