Lacrosse training isn’t simple like it used to be. If you want to play at a high level, you can’t just play backyard games. You generally can’t even only play for your school team.
You may consider going to a private school that has a more competitive team and/or also playing for a club team. You also will want to make sure you’re putting in extra work to improve outside of those practices and games.
You may work with a skills coach, a strength and conditioning coach, nutritionist, mental performance coach, and then athletic trainers and/or physical therapists if you get injured. Each person you go to will give you some suggestions on how to improve. The trouble is, how do you figure out what to prioritize?