Continuity mistake: When T.J. goes back to the school to investigate the green light, you will first hear him say "9:20." Then a few shots later he says "9:23 and a half." Then one shot later, you will hear him say "9:22 and a fourth."
Continuity mistake: In the scene at the treehouse when the kids are eating ice cream and scattered around with spoons, Cretien is not eating ice cream she says "Guys.. aren't we supposed eat supper before desert?" after she says that all of a sudden there all sitting around each other and Spinelly and Guss are missing there spoons.
Continuity mistake: When all the kids first break into the school some of them throw water balloons at the guards, when the guards chase after them they're dry.
Plot hole: Summer vacation couldn't be taken away just because it is winter, (or just snowy), they could just go by the date.
Factual error: There's not enough soda in two cans to soak two ninjas.
Continuity mistake: In the scene where T.J. and his friends are getting ready to break into the school, T.J. zips up his sweater. However, when the camera cuts out to a shot of the entire group of friends his sweater appears to be unzipped once again.