Not so long ago, student debt was mostly the responsibility of students. That is, you paid for college with loans and then paid off those loans with the proceeds of the good job you got with an advanced education. These days it’s a little different. The cost of higher education is soaring, the jobs available to college grads don’t pay as much, relatively speaking, as they used to, and the size of loans available to students – though huge – don’t cover the full cost of many degrees. One might expect these changes to lead more students to work for...