Jinns don't eat human flesh. Ghouls do that. You can't confirm its a ghoul either way. They don't like to hangout on the 4th floor of populated buildings. If a ghoul is hanging out in your classroom you'd probably be dead already. But if birds can fly into the building, then chances are its left over prey. Birds will pick apart the tasty bits and leave the carcasses on the ground. It could also have been a dead rat or the remains of one or just something someone puked up one day. Only way to know for sure is to examine the flesh.