Someone else's name

For the first time in my life, I entered a school. But it has no windows, the doors don't lock, and monitors are scurrying all around... And I must survive in this closed school under someone else's name. I am sure there is a traitor among the students who is just waiting to reveal my secret. But how to find this out and survive? I promised my parents that I would help other third, forbidden children like me. And I will keep my promise.