How to impress my football coaches?

I'm 16, 5'8 and half, 145 pounds and I play cornerback. This is my first year playing football for my high school team. The other day, the coaches had to choose 20 people to go on a 7 on 7. I wasnt chosen. It seems the coaches play favorites because theyve known the others since middle school and Im the new kid on the block. Eve though I do just as good if not better than the other corners chosen, they never seem to notice. What can I do to impress them so I can start varsity this upcoming year. When they didnt pick me I felt depressed because it made me feel as though Im not good even though Ive proven to myself that I am.