What Deliverance said and for future - remember to open the teleports on each location so you can use them. I mean you have to talk to the teleporter npc and click the teleport option to open the list of possible teleports to activate it. It should open them just by talking to the npc but I've noticed that it doesn't always work.
Your problem now seem to be that you teleported to Astral Academy without having Novograd or any other teleport open - thus you can't use the Academy teleport, which would normally work just fine. However, if you had Novograd or some Lightwood teleport open, it's weird why you can't get out.
PS. If you don't have Novograd teleport opened, you may have a black stone in your bag. You get the Adventure Stone (in your character gear view, press i ) after you have talked with Novograd's teleport npc. In theory, that black stone should still be able to teleport you - however, I'm not sure does it take you back to Evermeet Isle or just to Novo. And I don't know for sure does the black stone work at all anymore.