That sounds nice but it requires there to be a definition of "societally high-reward education". That is difficult. Even if you find some methodology to identify the quality programs that have an appropriate "societal reward" you have to deal with the problem that the costs for those programs will inevitably rise in lock step to the amount of tax dollars used to subsidize them. (See https://www.newyorkfed.org/medialibrary/media/research/staff...)

I would suggest the federal government get out of educational loans entirely. Let the private loan market evaluate and take the risks, probably with an income based repayment contract that favored degrees/programs that are likely to lead to reasonable incomes.