College costs keep rising. More students pile on student loan debt to get through. It?s a much-chronicled story in higher education. But a new study by UW-Madison professor Jason Houle reveals surprising findings about who gets soaked the most by these trends. It?s not the poor. Or the rich. It?s the middle class. On average, students from middle-income families leave college with $6,000 more in loan debt than their peers from poor families. Compared with higher income peers, the difference is even greater: middle-class students rack up $12,000 more.