In Maryland, at least, Catholic schools aren't required to have “certified teachers” teaching class. At my high school alma mater, perhaps 20% - 25% of the faculty have teaching certifications and/or education degrees.
The rest have degrees in, oh, say, chemistry if they're teaching chemistry. Or math, if they're teaching math. My son's Latin teacher has degrees in history and ancient history. He's working on his Ph.D. in Early Christian Studies, and thus is fluent in Latin in Greek. So, he teaches Latin, Greek, and Ancient Classical History. Go figure! ;-)
sitetest
Yeah, I'm sure state laws have a lot to do with it, and vary significantly across the board.