Continuity mistake: While the four guys are on their way to Detroit, Trip is hanging out of the sunroof. In the next few shots, you can clearly see that the car has no sunroof for Trip to hang out of. [The Volvo does have a sunroof the whole time, it is actually a moonroof with clean lines that are hard to notice.]
Continuity mistake: In the toilet scene one cheerleader pulls her panties down. They slide to her feet, but in the next shot they are a good 15cm up from her ankles. Unless she can make things rise with her mind, that's not supposed to happen. Also when her panties slide down her legs there is a sound of someone lifting a toilet seat, but she is already sitting down. (00:18:00)
Continuity mistake: The brake pedal on the Trans Am is first shown with chrome trim around it when the driver stomps on the brake to cut off the Volvo. When the rock is put on the gas pedal to send it into the ditch, the brake pedal is seen to have no chrome trim.
Factual error: The Pizza Pig delivery driver arrives to the parochial school in a pink Lada Niva. Russian Ladas have never been imported into the States, and though it may be argued it have been purchased and brought into the US from Canada, since Canada did import them for awhile, the Lada is a late 80's model, and the movie takes place in 1978.
Factual error: When Beth is looking out the school window at Jam's Mom driving away with him leaving the school, at the top of the screen is an adjacent street and one of the cars passing by is a Chevrolet Venture minivan, which didn't come out until the mid 90s. (Note: this error has since been cropped away from DVD and Blu-ray versions and is only visible on the VHS release).