When I ended my relationship with my alcoholic boyfriend a number of years ago, my income dropped by 50%. At that point, I sat my teenaged daughter down and told her that I could take care of our daily living expenses, but she would have to foot the bill for college when the time came.
Knowing that she only had herself to rely on, she took it upon herself to teach herself programming and web design and used those skills to start her own online gaming company at the age of 15 with the goal of raising enough money for college. Well, that small business grew and grew and the money started pouring in. Newspapers and magazines began featuring her online game and she became known in the computer gaming world long before she ever entered college. So when it came time to apply for colleges, she had her pick to choose from.
That game put her through college where she just completed her bachelor's degree in programming. And since she was paying for her own classes, she had great incentive to get good grades. She didn't want to have to pay for any classes twice. She accepted a job with a software development firm a few months before she earned her degree. At 22 years old, she's making nearly the same salary as I am, and will exceed that in no time at all.
I was one of seven children and my parents couldn't afford to send all of us to college. The only fair thing to do was to send none of us. We each had to put ourselves through school, and we did.
The moral of my story is that when parents take on responsibilities that belong to their children, they may grow into dependent adults. When parents back away and allow their children to sink or swim on their own merit, they're more likely to become self-reliant, independent adults.
Your son knows what his responsibilities are in regards to his school work and athletic activities. Let him sink or swim on his own merit. He may just surprise you.