You are aware that Christian colleges existed for years? They have pretty large tradition.
However, many of them are unpopular outside that demographic, because they enforce quite serious restrictions on students. You can be kicked out for having sex, drinking, for cloth you wear and quite a few other infractions that don't exists elsewhere. Teacher can't be divorced or omg single parent either.
As bonus, all discussions about free speech of students in what you call progressive school are quite funny, if you compare it to large speech restrictions students in Christian school have to follow.
It varies widely from one college to the next, and perhaps also with the general social climate.
I attended a Christian liberal arts college in the early 80s. I didn't belong to the same sect as the college, and wasn't particularly religious. The college had strong science programs, which is why I was there.
It was kind of an interesting time, with "fundamentalism" coming into broader public visibility, the Moral Majority, and so forth. This seemed to matter more to the students than to the college. I remember listening to late night debates in the dorm about whether the college's sect was "fundamentalist," and what they should be teaching about evolution, rock music, and so forth.
Naturally there was a religion department, and the college also contained the seminary for the sect's ministers. Officially, I had to take two religion courses, one of which was pretty much an outline of the sect's doctrines (which I've forgotten), but it was a required course, so it had to be easy enough for everybody to pass. And my Econ 101 professor taught about "Christian economics," which turned out to be Reaganomics, including the Laffer Curve.
Almost all of the region's small colleges were sectarian in some form or fashion, but varied widely in terms of how visibly religious they were. My experience was decades ago, and the alumni magazine that I get from the college suggests that they haven't changed much with the times. I'm not sure I'd choose a religious college today, or recommend one to my kids.
Catholic schools in particular tend not to be nearly that strict.
Nobody would mistake Georgetown, BC, Villanova, Fordham, or Notre Dame for somewhere like Liberty University. Indeed, the campuses would be ghost towns if some of those rules were strictly enforced.
However, many of them are unpopular outside that demographic, because they enforce quite serious restrictions on students. You can be kicked out for having sex, drinking, for cloth you wear and quite a few other infractions that don't exists elsewhere. Teacher can't be divorced or omg single parent either.
As bonus, all discussions about free speech of students in what you call progressive school are quite funny, if you compare it to large speech restrictions students in Christian school have to follow.