Okay, so I set up my dungeon XP farm perfectly but for some reason when I try to slay the skeletons, they don't drop a single orb of xp. They drop all the mob loot, but no xp. Why?
Are you actually sure.. ? : ) Is there a chance that you have something with Mending enchantment on you or your hand?
Is this in singleplayer or on a server?
If on a server, could they have a plugin that disables XP from spawners?