You are prudent and cautious for good cause. It is not uncommon for young people to be 'impressed' with the adverse opinions on matters of faith when they are introduced to such at a young and impressionable age. Many times even the best Catholic College can be a dangerous place spiritually as there are those professors etc. that seem to think that in order to 'teach well' they must first challenge all that the child brings with them from their former life as a child in a family of believers. I have even heard a priest who was a teacher in a secular college wax poetic about the need to 'tear down all that the young person believes to be true in order to rebuild the young person to be more enlightened and open to the opinions and diversity of the world'.
My best advice to you would be to enter into the college of your choice with eyes wide open. Stay close to your son through constant loving and attentive communication that is neither restrictive or combative. Be aware that many times the questions of faith that do arise are not necessarily red flags that a young person is losing their grounding but that they are eager to discuss with a person they love and trust those issues that may at the time be confusing and distressing. Ideally it would make sense to have your young son stay close to home physically as then you are better able to be active and involved in his experience. Many times when young people are far from home they feel isolated and disconnected from the roots of the family and the family morals. In this emotional state they may seek the unholy advice or counsel of those who do not have their best spiritual interest at the heart of their discussions.
Above all pray, pray, pray. Trust in the Lord's great mercy and overwhelming desire to see that all comes to good for the glory of the Lord. Allow that there will be 'rough water' now and then but this is not the time to jump from the boat. Stay connected to your faith and allow the Lord His time in the life of your son and your family. This may mean that through adversity and challenge you are better able to work through the issues that may or may not arise. Be watchful and vigilant and trust in the Lord.
My husband always says 'Hope for the best and pray to meet the rest.'
Let us offer our prayers this morning for all those families that find they are estranged from one another through misunderstandings or challenges that have been introduced at the hands of others. All these things we ask in Your Precious and Most Holy Name, Jesus.
Sending out a prayer,