On PC you need to clean out these folders:
- [Academy folder]\game\saves
- C:\users\ [username] \AppData\Roaming\RenPy\ACADEMY34-v0.2.3
First one contais saves for the currently launched version, and the second one contains synced saves across all versions.
On Android you have to check these folders:
- SD:/Android/data/[something with academy in it]/files/saves/
- [Your local storage]/Documents/RenPy_Saves/[something with academy in it]
However, on Android saves should get deleted alongside the game.