I'm surprised private schools have a lower default rate, since they cost more. I suppose people who attend private school come from wealthier families on average?
The big for profit schools sound like a big name but aren't. Like University of Phoenix.
The sad fact is: the typical American doesn't even do enough research to know if they are going to a private for profit school or a prestigious state school.
They are just happy they 'got into college', nonethewiser that the school they got into is a money trap.
That is not what the data says. The data says that public universities have the lowest. But public and non-profit private are very similar, so the real split is probably between private for-profit (i.e. scams) and everyone else.
There are probably plenty of reasons why wealthier families attend prestigious private schools even if tuition were free, perhaps the most conspicuous being the high profile bribery scandals.
Private for-profit - Joe's No Good Truck Driving School - maybe 25% or even 50% default
With a spectrum in between depending on quality of school and area of study.