When President Obama signed an executive order this past week to allow millions of student-loan borrowers to cap payments at 10 percent of their monthly income, he addressed the largest pile of debt burdening Americans: Collectively, we hold more than $1 trillion in student loan debt, more than all the credit card debt in the United States. “It has become clearer and clearer how important higher education is to our economic future,” White House domestic policy adviser Cecilia Muñoz said Tuesday. “It has also never been more expensive.” But in Maryland, public university...