Maybe consider a summer program next year instead ?
There are other threads answering your question but I can’t find them. Someone else may.
If I were local, I’d cold call office hours. Sales 101 and that’s what you are doing is selling yourself - get in front of the decision maker. Office hours gets you in with no gatekeeper.
Now the school may have a rule against having non students or underage people.
But I used to be in outside sales. The hardest thing and most important thing is getting to the decision maker. Many struggle to or simply don’t know how to say no. So go meet them face to face, unannounced when you know they’ll be there.
Another thought - see if your teachers have professor connections or experience / knowledge of previous kids.
Finally - maybe be a kid and do kids things instead.
Good luck.