Rock n roll high school is a classic, but it is a full on comedy and requires a certain kind of sense of humor.
If you don't like documentaries or concert films there really aren't many "punk" films that i know of. You should really think about watching some documentaries though. There are dozens of great punk doc's.
Otherwise i would recommend
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Tapeheads is also a great movie. I don't know how "punk" it is, but its kind of punk i suppose. It's about as punk as "pump up the volume" with Christian Slater. That is also a movie you should check out if you havent seen it yet.