First of all, Catholic schools are not “private schools” in the ordinary sense - they are still governed by the Schools Act, and are required to hire teachers with accreditation from recognized University programs, with at least a BA in their preferred subject area, and a two-year teaching degree. This is the minimum standard. They not only wouldn’t hire anyone less qualified than that, legally, they can’t.
That depends ENTIRELY upon where you are. I’m in California. Here…Catholic schools, like all other private religious schools, may hire whom they please, credentialed or not. In fact, having looked at several Catholic school "salary schedules’ posted on the internet, I find that a good percentage of the teachers are NOT credentialed. In one diocese, which I will use as a typical example (Fresno) they want new teachers to be credentialed, but all they really need is a BA/BS and a passing score on the CBEST. They need to show a plan to get their teaching credential within six years of first hire, but that plan may be extended. Within four years of hire, they must get a “Diocese of Fresno Catechist Certificate.” I don’t have a clue whether one can do that and not be Catholic, but please note: California public schools have the option to hire people who do not have full credentials. They are hired as “interns,” but they must be currently in a credentialling program, and have the credential within TWO years of first hire.
In fact, here are the requirements for the job of PRINCIPAL in the Fresno Diocese schools:
Have a BA from an accredited college or university
Completed the CBEST
No criminal history
Be an active and practicing Roman Catholic
4 years of ‘successful’ teaching experience, preferably in a Catholic school
Be committed to the ministry, philosophy, and goals of Catholic school education.
In other words, a Catholic school principal need only have the minimum qualifications required of a public school subsitute teacher. (The BA/BS and passing the CBEST), be a good Catholic and have taught Catholic school.
Neither - I would prefer that the school continue to advertise the open teaching position, and wait for a qualified Catholic candidate to appear, or else leave the position vacant and combine classes.
That would be one option. It is, however, not always the option taken by the school.