One fast-growing American industry has become a conspicuous beneficiary of the recession: for-profit colleges and trade schools. At institutions that train students for careers in areas like health care, computers and food service, enrollments are soaring as people anxious about weak job prospects borrow aggressively to pay tuition that can exceed $30,000 a year. But the profits have come at substantial taxpayer expense while often delivering dubious benefits to students, according to academics and advocates for greater oversight of financial aid. Critics say many schools exaggerate the value of their degree programs, selling young people on dreams of middle-class wages...