That's fine.
Their opinion is fundamentally irrelevant. Whether a teacher can be fired over conduct is entirely based on the codes of their profession, their agreements with their union, and so forth. A lot of parents being upset is not cause for termination, not unless his behaviour broke one of those official rules.
This wasn't a private religious school, it's a public school. I already linked their website. They're part of the Cumberland County Schools system, specifically.