so, with the debt thing, to clarify.

the goal should be as follows:

1) public universities should be subsidized entirely by taxpayers.
2) it should be hard to get into these schools, and they should regulate their supply of professionals based on what statistics regarding market demand exists for them that government can conjure up. so, free university shouldn't mean an influx of fine arts grads, but should also mean a more centralized production of professional workers.
3) private universities should eventually be phased out.

so, the reason you leave the private school debt in place is because you're ultimately trying to nationalize these schools. universal debt relief doesn't make sense in the broader context of this, unless it comes with a total socialization of education, which nobody is currently talking about. but, in the end, it's that socialization that you really want, and what the policy ought to be angling for.

if you set up a system where one type of schooling is "free" and the other one isn't, the expectation should be that the best students will gravitate to the least expensive option, so long as it is just as good, leaving for profit schools for legacy students of the rich and stupid. that is, you set up the public schools to push the private schools out of the market, over time.

so, i'm not concerned about income as a dividing line, here. i'm not complaining about giving hand-outs to rich kids, or pushing for a "progressive" approach over a socialist one. what i'm doing is pointing out that the universality doesn't make sense so long as the market continues to function, and that if you're going to leave the market in place you should be starving it rather than funding it.

so, go ahead and bail out the public school students, but make it clear to everybody that private school students will receive no such treatment, not now and not ever in the future, either.