In many states private schools don't need the same certifications as public institutions [1]. I'm sure they would prefer it in applicants but beggars can't be choosers.
[1] https://www.pa.gov/agencies/education/programs-and-services/...
Yep. And that's why charter schools, school vouchers, and private schools are the manifestations of desire for those wishing to destroy and defund public secular education.
Do the certifications mean anything in particular? Beyond perhaps the primary grades, I would settle for mastery of the subject matter and an ability to manage the classroom.