Continuity mistake: During the General Patton speech before the football game, "Gill Harris" approaches a player wearing the number 19 on his jersey, who is black. During the football game you notice the player wearing number 19 on his jersey is now white. (00:45:45 - 00:47:00)
Continuity mistake: When Gil shows the band the yearbook up close, Courtney's photo differs from the wideshot of the yearbook. Also, in the close-up there are two guys on her left and right, but in the wideshot the one on the right is now at the top left corner of the page. (00:32:30)
Answer: That's SR-71 covering Gap Band's "Let It Whip."