Most "grown ups" in the video, obviously, are the Nada Surf band-members, all the others, including the cheerleader girls, were amateur actors - probably casted at the school the video was shot at. All what's known about the cast is on the Clipland page for the music video: Nada Surf - Popular

Regarding the boys, one seems to be named Dave, the second guy. The other one, with the long dark hair, sadly already passed away...