Continuity mistake: When the guy get up and shouts "Janey's got a gun." there is no one behind him. When it cuts there are suddenly two people painting behind him. (00:31:15)
Continuity mistake: At the end of the song when they all pose with their hands in the air, some of them have different positions (head tilted a different way, different leg forward, etc.) when the camera does the panning shot from above. (01:04:35)
Continuity mistake: At the end of the movie when Janey shushes Jake her finger pushes his lip up. When it cuts her finger is just laid across his lips. (01:21:25)
Continuity mistake: After the twins are announced as prom queens it shows a close-up of Priscilla, who stands at the front of the crowd (closest to the stage). When the twins walk up the stairs, Priscilla is no longer there. (01:09:15)
Continuity mistake: When the boys are watching the girl use the loo, it shows a shot of the ceiling in Janey's classroom (just before the vent falls) and the ceiling is smooth, but when they fall you can see a part of the ceiling has been replaced by some loosely placed white bricks, which would fall easily. When they're on the floor with the turd all over them there are no bricks in sight.
Continuity mistake: When Jake and the twins are dancing the girls' hair is together in the space between their heads. Jake looks through the space and it is suddenly clear (the hair looks pulled back). (01:10:00)
Continuity mistake: When Jake goes to ask his sister for a favor, she takes off her robe and hops on the bed, spinning clockwise. In the next shot she is in mid-air, but there is no twist to it - she hops onto the bed straight. (00:30:30)
Continuity mistake: The stupid fat guy's supposed to die because he had so many concussions, but in the scene after the football game when he's on a stretcher and it collapses in the background you see him putting his hands out to make sure he doesn't get hurt during the fall.
Continuity mistake: When Catherine is taking off Janie's glasses she leans right in, but when the camera angle changes it shows this to be a larger gap. when the camera flicks around again she appears to be leaning in again.
Continuity mistake: In the scene where Jake walks into the cafeteria and Austin makes fun of him ("he has a thing for butt ugly girls") there are a stack of wrapped sandwiches on sliced bread in front of the fat guy. A moment later, they are unwrapped sandwiches on hoagie buns. (00:49:20)
Continuity mistake: In the scene where Jake enters Janie's basement where she is painting, (after he says there was a hole in her house) the paint on the brush is red, in the next shot it is greeny-blue. She would not have had time to clean the brush as the different shot lasts for about 3 seconds.
Continuity mistake: During the football game, Jake is wearing a Nike shoe (black with a swoosh). After the game when talking with Janey it's got a cross-hatched design. (00:57:40 - 00:59:25)
Continuity mistake: In the scene where Jake asks Janey to the prom, Ricky puts his fist to his mouth after she says she will go with Jake. It cuts to a shot where he has nothing in front of his mouth. (00:51:10)
Continuity mistake: At the end of Jake singing "Janey's got a gun," he has the microphone angled away from the microphone stand. The shot changes to the guards giving Janey a taser. When it comes back to Jake, the microphone is angled back toward the microphone stand. (00:32:55)
Continuity mistake: When Mitch is giving the the letter to Amanda, take a look at her hairs: it switch places between scene. (01:29:01)
Answer: The song is called "Yoo Hoo" by Imperial Teen. The same song plays in Jawbreaker when Rose McGowan is leading her friends down the hall, which is of course, the scene that Not Another Teen Movie is mimicking.