And what's this about "theological differences"? Could these parents have been so clueless that they don't know the differences in belief between the Catholic Church and the Reformed Churches? Even if they've now figured that out, wouldn't the serious "differences" be over issues like transubstantiation or the sacraments instead of a pop song?
I'm a Presby parent of kids in Catholic school and I knew exactly what I was getting into. We are guests and follow the school rules. My kids have been treated with respect and courtesy. Frankly, the "theological differences" have provided an opportunity to discuss the great common ground we all have as Christians and to contrast our differences with the Catholics. My kids probably know more about Christian theology and the Reformed faith than 90% of their fellow PresbyKids.