I attended a graduation this year at a private school in Austin and noticed that the program listed two students who were attending this "university." Of my relatives who have graduated from this high school so far, both have gone to excellent colleges and are pretty normal kids. And while the small, religious-focused curriculum surely contributes to the decision to attend such a purported institute of higher learning and truthiness, I have to suspect that the parents of these kids have a ton of influence on their destination. Because the school seems perfectly capable of getting a lot of its students into good universities.
Of course, as Ty Webb said, the world needs ditch diggers too, and, by that same token, no matter the school, some of the kids just aren't rocking it academically. Still, there are better colleges, and even the dimmest bulb at one of these expensive, private high schools can be leveraged into a decent, state school.