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.

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“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