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It must be Portage since there was a P on the uniforms. There also were some drum majors (but no band) who were all men and wore kilts. I assume they were from Bishop McCort because the kilts were in McCort’s colors.
You won’t guess the actor from looking at IMDB. Slap Shot was written by Nancy Dowd, who based it on her younger brother Ned Dowd’s minor league hockey days. One year after Slap Shot she won the Academy Award for Best Screenplay for “Coming Home”. Something happened after that. She continued to write and collaborate on screenplays but did most of them under a pseudonym or without on-screen credit. For example, she collaborated in the screenplay for Ordinary People but got no screen credit or share of the Oscar. There are lots of disputes in the industry over writing credits because many times the person who writes the first draft ends up having very little of it in the movie. Sometimes, even the “final” script is “polished” by another writer or the director (Tarantino is well-known for doing that.) Those disputes are settled in arbitration by the Writer’s Guild. (If you see credits with something like “screenplay by A & B from a story by C adapted for the screen by D” that is almost certainly the result of a Writer’s Guild arbitration.)
The word in Hollywood, for which I have no factual basis other than a former client who was a novelist and screen writer (you might have seen Get Shorty) was that the Writers Guild decision on Ordinary People denied her co-screenwriter credit, she thought the decision was sexist, refused any credit at all and began writing under the assumed name of Ethan Morton, with the Ethan being from Ethan Frome.
Anyway, as an homage to Slap Shot, the producers of Mystery, Alaska asked her to do a cameo in one of the crowd scenes in the new movie. She declined, but suggested her brother Ned, who did it but is uncredited. Ned played the arch villain and convicted criminal hockey player Oglethorpe in Slap Shot.