Well, the issue with the Principle is that his actions violated the policy of his employer, the school board. I guess the same would apply to your question. Do some churches have policies against their Pastor's, or other senior administrators, doing party affiliated political work? I don't belong to a church, so I don't know the answer.
My pastor is an election judge. A school cannot have a policy regulating what outside religious activities a principal participates in. The school doesn’t own its employees. We will probably never agree, but the school didn’t fire the teacher who normally leads the group, only the principal when he filled in. Wonder why?