Actually, you can no longer request to go from Obelisk to Slifer, or etc etc anymore.
You must be tested and a decision is made according to your skills in the duel.
Reason being, I presume, is that the staff doesn't want like our 10 best duelists wanting to go into slifer so that people will think they are weak, duel them and yadda yadda yadda. ;P Example being Chaos, with him flaunting being a slifer and dueling a lot of people because they thought he was a nub.
Spore. Grapha. Is. Not. A. Puppy.