Schools should be secular, unless it is a private school owned a by a religious body. Religion is a private affair, practised by the family at home.

It certainly can result in a kind of apartheid with children being discriminated against because of their affiliations. 

It should be relegated to a society or club which you can join, and meets before or after school, like any other extra-curricular interest.

Otherwise, let's be all inclusive and have politics at schools, too.