Chemistry 1: Firecrackers available from chemistry set
Chemistry 2: Stink Bombs available from chemistry set
Chemistry 3: Itching Powder available from chemistry set
Chemistry 4: Items produced doubled from chemistry set
Chemistry 5: Chemistry set available all the time

English 1: Apology improved
English 2: Better taunts
English 3: Ability to apologize to prefects improved
English 4: Ability to taunt bullies more effectively and from a distance
English 5: Ability to apologize to police

Art 1: Able to exchange gift for a kiss from a girl
Art 2: 50% health bonus from kissing girls
Art 3: 75% health bonus from kissing girls
Art 4: 100% health bonus from kissing girls
Art 5: Ability to kiss girls without giving gifts

Gym 1: Headbutt and 3-hit knee groin combo unlocked
Gym 2: Accuracy for slingshot improved
Gym 3: Kneedrop unlocked
Gym 4: Accuracy for slingshot improved
Gym 5: Accuracy for slingshot improved