To the people saying it's the coach's fault if the team is down this year...have you ever coached high school??
I've coached at 3 different high schools. We've had great success at each...some years. But when a bunch of kids graduate, or a promising sophomore moves, or a couple kids end up hurt, it can make a big difference.
Think about the best coach you know. Is their entire team made up of high performers? Of course not. And that's not because the coach sucks. There are always going to be slower and less talented kids on the team (which is fine), and for various reasons outs of your control as a coach you might lose talent from the year before and not have a pipeline of future stars ready to step in and fill their shoes.
Anyway, I always enjoyed coaching the middle and back of the pack kids, BUT, I admit that it was a lot more fun when I also got to watch some fast performances.
I'd suggest just doing what others are suggesting and try to get more satisfaction from the individual improvements and make sure you aren't getting down. The kids will pick up on that, and you're gonna want as many coming back as possible if you're rebuilding.