I wasn't doubting what you said at all, I just find it so upsetting to hear that this is the case in places. I'm from a small country in Europe and went to a Catholic school but this was definitely not the case at all, there were even students who were pregnant in their teenage years. I do think it's a very backwards way of thinking :(
It was like that in my Catholic secondary school as well. Evangelical schools are hard core, very scary (not all of them). Obviously they can't stop students from getting pregnant (or having sex), so that's why they have a policy of only hiring married people. They're also the schools that ban certain books (because obviously).
For the secular, private institutions it's more of avoiding "scandal".
In some countries would you really have people saying you are unfit for a job because of a pregnancy outside of marriage?? Just genuinely curious