Continuity mistake: In the scene where Dewey and Ms. Mullins are in the bar, the shots from behind Ms. Mullins sitting down show that her left hand is on the table. However, the shots showing the front of Ms. Mullins show her arms folded.
Continuity mistake: As Zach is 'raising his goblet of rock', his hand gets a lot lower in a shot change. (00:40:10)
Continuity mistake: After the kid's music class and Jack Black yells "You." to Zack, you see the kids around him sit down twice between shots.
Continuity mistake: During the scene where the kids are saying their version of the Pledge of Allegiance, the camera zooms in on a blonde girl. From shot to shot, which hand she has over her heart changes.
Continuity mistake: As Ms. Mullins says, "You know, it's more complicated than that" she brings her right hand up above her shoulders, but in the next shot, her hand is lower. (00:37:30)
Continuity mistake: During the scene at lunch when Dewey is telling the teachers a story, we see that the teacher who is sitting at the end of the table near Dewey is pretty close to him, but after Dewey tells the "gym teacher joke" we get a view of the table and the teacher that was nearest Dewey is farther away than before. (00:49:00)
Continuity mistake: Watch the top of her handle of Ms. Mullins' beer before she takes first sip. The level is high. Then look at the glass handle after Dewey gets up. The level is even lower but she never drank any more. (01:08:05)
Continuity mistake: When Billy gives Dewey the paper bag with his clothes in it, towards the end of the film, the way the bag is folded at the top changes between shots.
Continuity mistake: At the beginning when Dewey gets kicked out of the band, he picks up his guitar case and raises it above his head. In the very next shot, from behind, the guitar case is suddenly down by his side. (00:07:15)
Continuity mistake: In the scene where Dewey tells the class that he is going to be singing and playing guitar, Alicia says something like "Why are you in the band?" and the shot is of her back with her right arm behind her chair, but when the shot changes so you see the front of her, her arm is in front of her chair on the desk. This happens several times. (00:31:20)
Continuity mistake: When Dewey is writing his name on the board, he begins writing and then erases the end to leave "Mr. S". In the next shot that shows the board, it still says "Mr. S" but it is in different writing.
Continuity mistake: When Dewey is eating a sandwich from one of the girls, the Saran Wrap around the sandwich changes between shots.
Continuity mistake: In the classroom scene just prior to the naming of the band, Dewey is seated with his feet on his desk playing his guitar. The two girls approach him with the SOR T-shirt. From their perspective (front) there is nothing near Dewey's feet, but when the view switches to Dewey's perspective, the rabbit on the desk is now only an inch or so from his foot. In the wide shot the rabbit is nearly a foot away. (01:02:15)
Continuity mistake: At the title sequence, after Dewey's solo, and just before he stage-dives, the camera cuts from him, to the lead guitarist, then back to him. In the first shot of him, he is just putting down his guitar. In the shot of the lead guitarist, the neck of the guitar is visible as if he was still holding and playing it, but when it cuts back to Dewey, the guitar has been put down, and Dewey has his shirt off.
Continuity mistake: The amount of beer in Ms. Mullins' glass keeps changing. It sometimes grows.
Continuity mistake: As Zach finishes singing the song he wrote, he has both his hands on the guitar, but in the next shot, his left hand is on his thigh. (01:10:55)
Continuity mistake: When Dewey is getting the stuff out the van after he subs the kids' music class, there is a brief shot of the back as he removes the guitars and the keyboard isn't visible. However two shots later he gets it out out of his van.
Continuity mistake: When Dewy is saying that they should keep the project under wraps, he has his hands on the Gibson SG. Camera cuts and now they are at his face.
Continuity mistake: As Dewey says "You hate teachers, is that what you're about?", the black bespectacled girl has her hand on the table, but in the next shot, her arms are crossed. (00:30:05)
Continuity mistake: When Dewey leaves the bathroom after hearing the kids playing in the music class his shirt is sticking out of his waist band then in the next shot while he's running up the stairs his shirt is stuck back in again.
Answer: The song isn't on the soundtrack, and I can't find anywhere in the film where Jack sings lyrics that even sound like Tears. I don't think it's true.