At/in the same?

[emsr2d2]

Could you possibly tell me which one is correct? They used to go to the same school or they used to go at the same school.

I'm glad someone else spotted that you had completely rewritten your first post. That is not a good idea. The rest of your original post has now gone and a lot of our responses now look like nonsense.

As I said in my first reply "They used to go to the same school" is correct.