Cooking club will give player’s the ability to quickly raise their reputation in the school by handing out snacks. It’s currently the quickest way to raise the stat, which is important as having a low reputation will make the game much more difficult (beyond making friends with delinquents, but this has not been implemented yet).
Drama club will give players access to gloves and masks, making it easier to hide their fingerprints and frame other students for murders. Masks also make your character unrecognizable to other characters. Masks will be banned from school after a single murder, though, so players do not abuse the tactic.
When part of the occult club, it takes NPCs longer to notice strange aspects about them, allowing insanity or bloodied clothes to go unnoticed for longer periods. It will also decrease the player’s sanity loss, which makes for quicker attacks (lowered sanity makes attack animations take longer).
Other clubs offer many more bonuses as well. Art club gives players a smock that makes NPCs not notice blood splatter, music club gives players a cello case to hide bodies in, martial arts club lets players instantly win physical confrontations, photography club will give players access to NPC information through pictures and make the club not suspect you, and science club gives access to a blood cleaning robot.
Sports club lets players freely carry sports equipment, and gardening club will let players carry gardening equipment. Both of these are similar, although gardening club may allow the player to bury bodies in a later update.