Is the college close enough to you that you could do a visit with him? Show him what life is like at college and how he needs to be ready for it?
I LOVED college. However, I didn't realize how much I would love school in college, so I didn't try hard enough in high school - so yeah, I'm that person BusyBee is talking about that wishes they'd gotten into a different school - especially now that I know I could have excelled there had I pushed myself more in HS!
As a kid, it's hard to see big picture.....and by the time we do, it's often too late

Hopefully he doesn't have to learn that lesson the hard way - like I did!