Here is the full list of all 43 The Academy: The First Riddle achievements.
Finish 10 sidequests
Attend the First Aid class
Get 5 right answers in class
Get 5 wrong answers in class
Take pictures of all your colleagues
Take a bath 3 days in a row
Take 3 pictures with the camera
Talk to every classmate
Find 10 hints
Flush the toilet and wash your hands afterwards!
Play 3 arcade games
Re-watch the movie about the baron
Make time for a study session
Take a bath
Solve 15 puzzles
Attend the Painting class
Solve a puzzle in less than a minute
Solve 5 puzzles
Finish the entrance exam
Make time for a study session every day
Solve 50 puzzles
Solve all the puzzles
Finish the game using no hints
Finish the game using less than 20 hints
Find 30 hints
Find 100 hints
Solve 3 paper puzzles
Solve all the paper puzzles
Solve 7 library book puzzles
Solve every book puzzle
Take a picture of a pinecone on a tree
Find the sculpture
Find the device
Find the hidden safe
Take pictures of all the butterflies
Take pictures of all blue birds
Take pictures of all the graffiti
Take pictures of all the statues
Finish the final exam
Save professor Wilson
Attend Self-defense class
Attend photography class
Attend the Writing class