I grew up in, and still find myself among, the Southwestern Baptist Theological Seminary culture, and am in touch with many current and former students and faculty through church and lifelong affiliations (my father was a graduate.) I find that the majority of them are now agnostic at best, and atheistic at worst. The number of them who consider the Biblical accounts of the Old, and many of the New, Testaments to be "merely stories to teach us lessons" is absolutely astounding. You'd think that they were pickled in a lifetime of attending a UU "church" from listening to them.
Many are ardent supporters of a purely evolutionist world view, completely discounting that a God of the Bible could have anything directly to do with how creation came into being.
Finally, I think there is a natural questioning and searching that goes on at that age---having taught that age group for 30 years---and many return to the faith (which they really didn't "leave") within 10 years. About the time reality hits them.