I Was Falsely Accused Of Sexual Assault, The Police Dropped The Investigation, What Do I Do Now?

Location: Pennsylvania

I'm 17 and dated a girl at my private high school from September 2024 to December 2025, In December she started dating my friend behind my back and then began to harass me and call me slurs.

A month after she broke up with me she made a report to my school saying I sexually assaulted her in April of 2025.

My school made a report to ChildLine and the police, then expelled me without giving me any chance to defend myself or tell me anything about the report. In the meantime, the girl told my friends and classmates that I had been expelled for raping, molesting, and abusing her (We had never had sex).

Over the next month and a half I was not contacted by investigators or given any information on the situation until the end of February when my family was told the police dropped the investigation. After this we contacted the school to find out what would happen next, when we met with them they told us that the girl would not face any consequences, that I would not be able to return to the school until the next year, and that they would not make any statement regarding the lies she was spreading about me.

As of now she is still spreading lies about me and since I have been ostracized from the school community I can't really defend myself.

The only evidence I really have to defend myself are our DMs where nothing like this is ever mentioned, and some pictures of us together post-April where she is clearly happy and not being abused.

And from what I've heard the accusations she is making constantly change and are not consistent.

I would like to sue for defamation but I am afraid it will get really expensive.

What options do I have?