When you get inside the school, click on the guy. You will be brought to a mini-game. The objective of the game is to outrun the principal.
When you win, you get two prizes a Paint Gun, which when used, changes the color of another person and a Whoopee Cushion, which when placed, if someone steps on it, it makes a sound.
If you are having trouble with the mini-game, below is a video tutorial of it!
Until next post everybody.