I’ve worked in the Catholic schools. Students and their families are asked to provide proof of their Catholicity ( support of the church, letter form the pastor, up to date with sacraments, volunteering in various ministries, etc. ) but the teachers, upon signing contracts are not asked these things. They ask “are you Catholic?” Yes. OK! You’re hired.
No one investigates if they are even practicing.
The DRE should be teaching this person’s class. Not all folks are cut out for it, nor do they really want to. We had lots of Catholic teachers that refused to teach religion. They said they didn’t know enough about their faith to do it justice.

Again, that’s just around here. Not saying every place is like this. Just in my limited experience. 3 states.