A lot of the filming was done at the high school in Lockhart, Texas. The football team was used and the city was told to show up for the football game and were given fake t-shirts to wear in the stands. (Since torn down - new school built.)
It was on the set of this film that Harry Jay Knowles first got wind of Peter Jackson making The Lord of the Rings into a movie. He urged Elijah Wood to go for it even though the actor had never read the book. Which Wood duly did, ignoring the news that Jackson was largely casting British actors and videotaped his own audition.
(at around 3 mins) At one point, the principal suggests saving money by reusing the set from "Our Town". The joke in this is that Thornton Wilder's "Our Town" has no set.
Tina Rodriguez: (at around 10 mins) the tattooed girl whom Marybeth asks where the office is, is director Robert Rodriguez' sister.
Harry Jay Knowles: (at around 12 mins) the bespectacled, red-haired teacher having his injury examined by Nurse Harper (Salma Hayek). Knowles, most famous for his movie news website "Ain't it Cool News," is a long time friend of Robert Rodriguez and a fellow resident of Austin, Texas, where this movie was filmed.