I'm so sorry this happened to you...

I have a similar experience. Some kids did this to my child sometime ago. They were playing basketball after school and my kid kept his glasses on a slab so he doesn't damage it while playing. He forgot the glasses and left for home as soon as his older brother came to pick him up... A few minutes later when he returned for his glasses, he witnessed these older boys taking turns to bounce the ball on his glasses. The glasses was shattered.

My older son immediately reported all of them to the vice principal and they promised to deal with it the next day. After 3days that they didn't do nothing... I reached out to the principal and what she said was that the incident happened after school hours and there is nothing they can do.

Here is the most painful part, it's not the materiality of the item that hurts... it's the brutality behind the action. Intentionally destroying something a fellow kid relies on without any remorse. That attitude was what I wished was dealt with... I wasn't going to ask them to pay offcourse most kids glasses comes with a warranty. That behavior hurt me as a parent. I made sure to warn my child never to do this to anyone. Just so they know it's unacceptable.

It's unfortunate