Before Monsters Inc., Mike and Sulley went to School
An excerpt:
The movie begins with Mike, as he and his class at Frighton Elementary tour the Scare Floor at Monsters, Inc. and he is inspired to become a Scarer himself. He works hard and gets good grades.
And he goes to Monsters University to follow his dream. Early shots of MU are great.

Mirrored from Until Midnight and Occasionally Later.