Real estate development was the first casualty of the Great Recession, but a half-dozen New York City colleges are in the midst of an unprecedented building boom. St. John’s University in Queens has already spent almost $160 million on a new student center and classroom upgrades during the past two years alone. Fordham, the New School, and John Jay College of Criminal Justice are all betting on big campus expansions. And over the next three decades, NYU and Columbia are preparing to shell out nearly $10 billion for academic and administrative buildings, dormitories, research labs, and even unrelated commercial ventures like a hotel and a jazz club. Yet just as some of these schools get ready to send shovels into the ground, a weakened economy threatens to undermine even the best-laid plans. Students and their parents are increasingly reluctant to take on debt, especially at a time when job security is in doubt, says Joseph Marr Cronin, a longtime university administrator and former Massachusetts secretary of education. It’s a trend that’s reflected in the growth of community colleges—which now account for nearly half of undergraduate enrollment—and online schools. “Today, there are four million students taking one or more courses online,” Cronin says. “You don’t need a building for that. All of a sudden, the market for the most expensive colleges could really stall.”