Here is the full list of all 13 Old School Musical achievements.
Could be better (B on all main score hard levels)
Failing the best grade with only one mistake, it's sad
If you keep retrying this level, you will succeed
Losing 5 times in a row in easy mode ? Really ?
You deserve this reward for your patience with Mehdi
So, the controller has buttons, you must press them
We give you this but please leave Matt alone
Chicken Republic seems to be too easy.
You finished the story mode. Spoiler : everybody dies.
It's nice to talk to everybody
It starts getting serious (A on all main score hard levels)
Ok, but everybody can do that (B on all hard levels)
A like Almost (A on all hard levels)