2: Clear out all of the bandits and pit wolves on the outside of the fort. there is an adept level door on the west side of the fort that you can use to gain access to the upper level.
3: Go inside the fort. The only entrance (that I know of) is in the main courtyard. There will be bandits as well as wolves and pit wolves inside cages, and one wolf and an ice wolf inside a pit deeper in. The pit and all but one of the cages are locked. The wolves will not turn hostile until you open the cages or attack them through the bars. DO NOT kill the wolves or open the cages yet!
4: Clear out all the bandits. In the deepest part of the fort there are some rats swimming around in a partially submerged room, just past the room with the pit. Kill them too.
5: Choose a wolf and open its cage, but not any other cages. It should turn hostile.*
6: Close the cage with the wolf inside. He won’t be able to get out, but you need to be quick to do this.*
7: Cast a spell from the school of magic you wish to improve until you’re out of magic.
8: Exit the immediate vicinity, and go far enough until you can wait (which shouldn’t be too far, and you shouldn't have to go outside to do this), and wait for one hour.
9: Your magicka should have regenerated. Go back next to the wolf’s cage. Don’t open the door, just spam the spell again until you’re out of magicka, then go and wait again, then come back and spam the spell again. Repeat until you acquire the desired skill level.
Since the game registers that you are in combat, you can use this to upgrade all the schools of magic that require you to be in combat. A couple recommended spells are: Bound Sword for Conjuration; Muffle for illusion.
If you have any recommendations for the other schools, please post them.
*: If you set the difficulty level to adept or above, you might be able to use flames or sparks to shoot it through the bars, though I have not tried this.
NOTE FOR 360 USERS: The wolves in the jail cells sometimes appear out of their cages when you wait. The ones whose cages haven’t been opened yet have this issue as well, but until you open their cages or attack them, they shouldn’t turn hostile. I’m don't know if this last glitch applies to PCs.
EDIT: sorry for the confusion on the topic. I meant to say Magic skills


