Ok nothing to do with fma but why do school libaries not carry manga

I know what you mean. My highschool has only a few mainly Bleach and Naruto.
I do know that in Middleschool it was because some of the manga has bad content (the whole blood, violence, gore, and smutty crap) so most of the books have to be review before being entered in.

well mine carries fma actually but yeah i get what you mean

Considering I assume the fact that Library books come from the schools funding I don't think they buy them with it..they just buy regular book mine probably does it to enforce reading regular books..rather than manga..why I don't know.

Probably because it's not "educational"