It doesn't sound like it was a "kick the NO people when they're down" thing so much as one of those weird turf protection things that you sometimes get with adolescents. The school's just been inundated with 200 new students; it's got to be overcrowded, and some of the old students might resent all the attention the new students are getting or something. I don't know anything about the relationship between the two cities or what their stereotypes of each other are; that could also come into play. (I could see, say, my rural WNY high school responding in [i]exactly[/i] that way to a knot of kids from New York City.)

That said, it's still disgusting behavior.