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