Glasses frames and frames are intact, why do lenses fall off? According to your description, I think these glasses must be full-frame or those plastic frames, right? Why did it fall? That's because the mirror frame is slightly deformed after uneven extrusion or collision by external force, and it is completely possible to fall off. So this situation is possible.

So now that the frames are in good condition and the lenses are in good condition, you can tell the teacher to take your classmates to the optical shop to put the lenses back, and then ask the staff of the optical shop to do plastic surgery on this pair of glasses and adjust the slightly deformed frames. This will not affect the use. It's totally unreasonable for him to ask you to pay. After all, you didn't mean it. You were pushed by someone else. If he hadn't forced you, it wouldn't have happened If your classmate insists on making you pay compensation, then the classmate who pushed you should bear the main responsibility!

The above is my personal suggestion, I hope it will help you. You can email me if you have any questions, or send me a text message in the station!