Other mistake: After they kill the alien/teacher and leave the school they pass one girl in a blue/green tee-shirt with a waterbottle. Just one scene later you see this girl again under a tree, suddenly in front of them.
Other mistake: When Zeke is examining the alien, he puts his glasses on to look down the microscope, but wears them at no other point in the film. Since microscopes can be focused to the eyes of the user, most scientists take their glasses off to use a microscope.
Other mistake: About 18 minutes in, the new girl from Atlanta is hearing who Stokely is from Delilah. Right as the angle is about to change, looking at Stokely, there is a weird out-of-place zoom.
Other mistake: While Ms. Burke appears fine at the end despite losing her head, Jon Stewart still has the eyepatch from earlier when he should be healed too.
Chosen answer: The Kids Aren't Alright - The Offspring.
Class of '99 - Another Brick in the Wall (Part 2).