Art (Mr. H) - Definitely his favorite, even if he spends his time mostly drawing here rather than working on his puppets.
Chemistry - A little below his level, but blowing things up is certainly cathartic.
Combat (Logan) - A class he devotes a very large amount of energy into; he won't let himself become soft and rely solely on the staff to protect him from his former comrades.
Drama (Rogue) - Another class he loves; puppetry is a dramatic performance art, after all! Although he's better at acting using his puppets, than himself...
Engineering (Tony Stark) - Useful for brushing up on his technical skills, even if he feels a little out of place sometimes since he considers himself an artist at heart. Secretly loves Dug and pets him when no one else is looking.
English (Emma Frost) - Required so that he can speak and write pretentiously to show off how smart he is.
Psychology (Mr. H) - Thinks this can improve his ability to read and understand other people in social situations.
Self-Defense (Dick Grayson) - He can't have his puppets with him all the time to defend himself...
Tactical Strategy (Tseng Chen) - A natural fit for a methodical planner like him. He was always the one who did the thinking ahead when it came to his Akatuski missions, after all.