Pro Bono means for free. I don't know how you find a a lawyer, carpenter or doctor to work for free. Perhaps a lawyer might be willing to take your...

It is private property. They don't need a reason to kick you off the property, and don't have to show you their evidence.

Yes it is "legal." Courts don't get involved in how school administrations run the schools. .............

Not successfully. First off, any such lawsuit is barred by law. Second, any such lawsuit would cost you thousands of dollars and likely take years...

Google underage teen scam, and then block the number and have no contact with them. ...................

It is not your first offense. You apparently committed numerous offenses. You need to speak with your parents and a lawyer, and only them.

No you can't. It is within their right to deny you entry.......................................................

This sounds like an absolute scam. Block all contact with them and don't send them anything............

It appears the officer changed his mind, which is certainly their prerogative. You need to deal with the ticket.

Any lawsuit would cost you far more than the amount in dispute IMO........................................