Hi! So I’m looking for one specific fic, but any are welcome! (Either Destiel or gen please!)

So Dean is Ex something (he had a team he use to work with) and he is now working as a teacher. There is an incident - I think some men had broken into the school with guns - and Dean keeps all of his kids safe and is badass. His team gets called in by someone (no idea who lol) I remember it being pretty long, but not if it was a one shot, it may have been a few chapters. Also pretty sure there was no pairing either.

Any help finding this will be very appreciated! Thanks! :)