>Another solution is to let you go to school for free and then pay a percent of all your future earnings back to your college, or at least in to a pool that pays for the next generation's college.

We basically already have that system. If you get federal loans (which most people who take out loans do--90% of all loan disbursements) you can sign up for an income based repayment plan.

You pay back 10% of your disposable income (income over 1.5x the federal poverty limit), for 20 years.

If you make less than 1.5x the poverty limit, you pay nothing.