Classic Winner- beat classic mode
Party Winner- beat party mode
Demo winner- beat demo mode
Basics In speedrunning- beat any mode in under 6 minutes
Endless Novice- 10 noteboos in endless
Endless Pro- 15 notes in endless
Endless master- 20 notes in endless
No bullying in the halls- principal catches bully bullying you
Wow wasn't that fun- complete any mode with all fun options turned on
Bsoda Pro- get 4 or more characters caught in a soda blast
Sweepin' time- ride gotta sweep for 30 seconds (he must be actively sweeping)

Baldi's office- "get a tip from baldi by seeing him in his office"
ok, this one. If you were in this community for any time, you'll know about baldi's hidden ending. Just get that and you get this. For anyone who might not know, you get the hidden ending by getting all answers wrong and beating the game.

Baldi's Song- "find baldi's secret funtime song"
Ok, so there is actually a secret funtime song in the game, however actually finding it is not how you get this. To get this achievement you need to get the secret ending of party mode.
Bring a dangerous teleporter to the second floor after the surprise you get after winning, and use it while on the second floor, it will warp you back to the first floor and you can find "NULL" in the principal's office.

Baldi's Basement-
There is a hidden ladder you can access in demo mode. using it gets you this achievement. To get to it you have to get all 7 notebooks with answering every question right(?) and then once you get all 7 the other 6 rooms where you got the first 6 will reactivate all the math machines, go to every room again and once you answer the 6th one right you will get a portal poster, use it in the room with the scissors poster on the wall to the left of the poster and you will be able to access the ladder to get the achivement.

NULL- ERR - *FILENAME_2* CANNOT BE FOUND

Glitches Galore- Beat glitch mode, you unlock this hidden mode by beating every mode, finding "NULL" in every mode and getting the "wasn't that fun" achivement, i won't spoil what happens in this mode.