Trying to remember a manga where there is a school in the sky and the only way to attend is to see it and when they get there they have to write one word on a piece of paper that becomes their weapon to survive.

Not quite sure but it might be Aphorism. The school wasn't in the sky though, it was just a floating island that some people could see that qualified them to go to that school.

“All the kids have always known,
that the emperor wears no clothes,
but to bow down to him anyway,
is better than to be alone.â€

-Arcade Fire

that's it thank you