Your examples are all over the map - some commercial enterprises, some not, some private clubs, some public accomodations, some exclusion based on ethnicity, some on race or sex. The response to each is not identical.
As far as this one goes, however - it is a "prom." There is no indication that it is simply an "invitation only" private party. The criteria for attendance seem to be (a) student at the school, and (b) white. It is no more "right" than saying "everyone at the school can come, except for the Jews."
That being said - yes, I do think that association based solely on skin color is wrong. Regardless.