No one? (Or the guarantor, who then isn't paid back.) That's what I meant by "bankruptcy." Maybe, if they had "skin in the game", they'd be more inclined to be more responsible in their lending.
Or maybe the answer comes in capping the amount that can be paid back on amounts given, so that after paying for $x for $y borrowed, or paying for Z years, it doesn't matter how much you have left (thanks to compound interest), the debt is considered "paid".
Either way, loans will be harder to get, yes. Fewer people will be able to afford school at its current prices. Schools will have to make a choice of cutting back significantly, or trying to cater to those students who can't afford loans that would have paid for Ivy league schools. Community colleges will have to be community colleges again, vocational schools vocational.
I do know that currently, schools don't care where the money comes from, and lenders (and guarantors) don't really care where it goes to, and each loan that is too much for the borrower to pay back essentially becomes a money printing press. We keep paying, and many keep going further in debt to them.
Our system now can not last forever. A quick Google tells me that in the past 35 years, tuition has risen >900%. That number will continue to balloon as large as possible, until there is reason for it to stop. Maybe those alternative education models Cuban mentions vaguely (we probably know well what we means), but maybe this is what changes it. Allowing bankruptcy.
As long as possible, schools will continue to take as much money as they can get, to offer more, and bigger. And so far, lenders/guarantors seem content to let every person take that loan, and put a noose around their necks, as we've been told since we were children "go to school, do well, go to college, do well, you will do well in life". And as much as people here may value independent drive and self-teaching, I think we can agree that "the system" very much encourages people to attempt a college degree.
At least when the multi-billion dollar banks got into trouble, they had two options: go bankrupt and strike a deal with those they owed, or get bailed out. People only have one, "keep paying." And at some point, that just becomes indentured servitude.