I can concur, having attended various schools around the globe growing up. In one nominally American school (actually run by Canadian Catholic brothers, but largely attended by boys of American ex-pats), calling someone a "Commie" was fighting words (i.e. liable to get you punched). In other schools if you called someone a "Commie" people would likely think you were very strange and/or drank too much of the Kool-Aid.