no matter how low I drop the grades it won't let me get extra classes. I even dropped down to 0% and got the ferret. Nothing is working. I also can't even get into the teachers lounge to start the quest. Room is greyed out. 

Sorry for the late reply. The Midnight route has been fixed in update 0.06. To unlock a location, you must first explore it manually. That is why it was not available in the quick menu.