I found many other instances on the web discussing the trend. As one example of the evangelical concern, Summit Ministries' website features an article on the issue. In it, they say:
"Each year thousands of Evangelical high school students take the Nehemiah Institute PEERS worldview test, a survey revealing their worldview perspective regarding politics, economics, education, religion, and social issues. Every year since 1988 our Christian students have been answering those questions more and more like Humanists and less and less like Biblical Christians...
According to findings published in a UCLA dissertation, Dr. Gary Railsback notes that between 30 and 51% of Christians renounce their faith before graduating from college."
The author goes on to interpret the meaning of the study:
"That means one out of two professing Christian youth are turning their backs on the 18 years of Christian instruction from their homes and churches and embracing the atheistic ideas of their professors."
This interpretation puts the blame on the 'evil atheistic college professors'. In reality, a strong majority of college professors in the U.S. consider themselves not only spiritual, but 'religious' (this is not Humanism). Furthermore, most classes never even touch on such subjects and in those that do, it is standard practice for professors not to do anything that reveals their own beliefs. More likely, contributing factors are the learning of raw facts about the world (which form foundations of our opinions), interactions with a wider variety of students and student groups with more diverse beliefs than existed in their home town, and the general inquisitive soul-searching that comes with that period in life.
It seems to me a more accurate interpretation would be that the conservative Christian mindset and worldview are based on such flimsy medieval reasoning that, for anyone not predisposed to want to believe it, all it takes is a few bits of rational argument and facts to overturn 18 years of indoctrination. You don't see the same percentage of conversion to such types of beliefs coming from people who are well educated and raised with Humanism. The reason for this has less to do with politics, culture, media, or 'evil influences' by either party than with the objective qualitative differences of reasonableness inherent within the two viewpoints - and how they each resonate within any healthy human brain, given a fair chance.
I didn't find any mention of the internet in these articles, but it seems to me that the internet will likely have a profound impact on society, including religion. I believe many of these kids raised in conservative, fundamentalist, or evangelical religious homes before went many years before ever interacting with people of other beliefs. Some out in small towns even get well into their adulthood without ever seriously examining or being exposed to alternate worldviews.
I remember asking about Buddhism as a child and getting an answer something like, "Oh that's those crazy people that worship cows and think when they die they're going to come back as dogs and chickens and so on".
But now we have young teens interacting with, reading, and learning about the viewpoints of many different worldviews, from their own mouths. This tends to have an overall effect of casting doubt over everything, which is a problem for fundamentalism. Perhaps the only way to "protect" their children from that evil 'doubt' will be for evangelicals to become extreme isolationists, similar to the Amish. I wouldn't be surprised if we see some small branch of this develop over the next few decades, but I digress.
Concerning this generation of teens, we should wonder how many will return to evangelical Christianity once they have children or grow older? I would expect some recidivism. Right now, these teen beliefs are residual, based only on exposure to a variety of contradictory views and typical teen rebelliousness. As humanistic as their beliefs may tend to be, most have never heard of Humanism per se. If Humanists hope for this trend to remain intact, they'll need to reach out to these young people and make sure their beliefs are informed by Humanist principles and philosophy, and not merely based on rejection of something else.
I have recently thought of writing something I plan to call "12 Things All Conservative Christian Teens Should Know", which might be helpful to teens (I hope). It will be in a very informal conversational style, not too long, and should be an easy read. I have all 12 things in mind, but haven't written it yet, so I think I'll save the details for now.