I don't have a subscription to the WSJ, so I'm just lifting this quote from Ezra Klein's Wonkbook. 

College debt is hitting upper-middle-income households. “Rising college costs and a sagging economy are taking the biggest toll on a surprising group: upper-middle-income families. According to a Wall Street Journal analysis of recently released Federal Reserve data, households with annual incomes of $94,535 to $205,335 saw the biggest jump in the percentage with student-loan debt from 2007 to 2010, the latest figures available…The amount borrowed by upper-middle-income families, meanwhile, has soared. They owed an average of $32,869 in college loans in 2010, up from $26,639 in 2007, after adjusting for inflation, according to the Journal’s analysis.”Ruth Simon and Rob Barry in The Wall Street Journal.