College is a time of spiritual challenge for many young people, and I'm sure we could do more to prepare them for the spiritual battles they'll face. Perhaps your letter will encourage other parents (and also pastors) to do more to strengthen the spiritual foundations of their young people, so they'll be better prepared for college's intellectual and social pressures.
At the same time, don't feel like you are a failure, and don't despair over your son's apparent rejection of God. Many young people go through the same thing, suddenly thinking they are the first people in the history of the human race to have all the answers to life's problems and mysteries! But they aren't - and in time many of them begin to realize it. Like the ancient writer of Ecclesiastes, they begin to realize that life without God is "meaningless, a chasing after the wind" (Ecclesiastes 2:11).
Pray for your son, that God will keep him from wandering too far down a wrong path in life. Pray too that God will put within his heart a hunger - a hunger that can only be satisfied by God.
Most of all, encourage your son to look with an open heart and mind at Jesus Christ. When he does, he will discover not only that God loves him, but that only in Christ "are hidden all the treasures of wisdom and knowledge" (Colossians 2:3).