To be honest, I think going to college/university is a great experience that will help sharpen and develop your mind, but only if you want to put the effort into it and know what you want to study.
How many kids at 18 know what they want out of life? Know what career they want? I know I didn't have a clue. In the UK, Mature Students are becoming more popular and welcomed because they have lived, they have experienced different things and they go to college/uni because they know what they want and will work hard to get it. I'm not saying that there aren't any teenagers like that, but I think it would actually be better to get some job and life experience before going to college and leaving it til a bit later. I've seen people in their 80's going back to college, so it's not something that is dependent on age!
I do think college would be a great experience in knowledge fulfillment, although obviously it depends on what exactly you want to learn.