As debates over “free college” and canceling student debt go on, two professors who study college costs are arguing for more-nuanced approaches, to ensure that federal taxpayers don’t end up rewarding states that have been starving public higher ed. To me, the most interesting idea in their new paper, “Moving Beyond Free: A College Affordability Compact for the Next Generation,” is awarding a Pell Grant “top-off subsidy” to under-resourced, high-impact institutions that serve low-income students.