That's very odd indeed. Um...mild prodding suggests his order spread to Germany in one of its original incarnations, even though he never got there himself. Maybe whoever translated the hymn left the chorus in Italian as some kind of bilingual homage to their patron saint? (I know it says he wrote it, but at the time Germany was fragmented and had a number of different dialects. That hymn is in recognisably modern German, which wouldn't have emerged for another couple of hundred years.) ...God I'm a dork, and a babbling one at that.

And yes, your high school does seem a bit 'interesting'. ~_^