I am also one of the youngest in my grade as hs starts 2 days after my bd... parents should have started me later
Don't let your age or size deter you. Work hard, look for areas of improvement daily, even if it's just one. Improvement can be in any area. Such as, did your movement improve, mental strength, emotional control, technique, footwork, speed, game plan execution, etc. Any area relative to mental, physical, stroke technique, strategy, tactical etc. Putting in the right kind of hard work every day, you can pass some of the bigger players down the road. Although court time is of primary importance, you can make gains even with workouts at home. Jump rope, push ups core work, squats, running with an adult in the neighborhood, etc. If you are in better shape than most of your opponents, that will be a huge factor in your favor.
There's lots of good books and video out there, seek it out, get recommendations from your coach. Hopefully you can get a lot of match play and have access to some good coaching. And always keep your primary focus on your grades.
You are young to be on here. As
LOBALOT asked, make sure your parents are okay with you being on here. While there are a number of well meaning folks here, this is the internet, be careful. All the best!