Sorry, I did not realize this was a school team. You are right in realizing that you are in tough situation with a number of senior pitchers, and most school teams have this proviso about summer ball at least in my state.
Changing schools does not sound like an option at this point, and there maybe other considerations beside baseball. On the ther hand you can use the situation to refine your craft as a pitcher. Work on your change-up and curveball, so that when a break comes to get on a better team you are ready. There is no "I" in team, but there is a "ME".
You need to get something out the situation other than loses. Choose major league pitcher that has a similiar style, chart his pitches, then see if you can duplicate his outing. This might make it more interesting. Keep working on you. The other guys may catch up.
I would not dis my classamates/teamates. Ian.