The National Association of Independent Colleges and Universities said the totals were unprecedented.
The association said even more colleges raised tuition minimally, with Catholic University raising its tuition and fees just 3 percent this year while the College Board reported the average increase for private, non-profit universities was 4.2 percent.
The Washington Post said the action is aimed at attracting those students who qualify for little or no financial aid but don't have the finances to pay for a private school.
But the Post said the decision can be risky for non-profits with high fixed expenses, attempting to hire skilled faculty and keep classes small.
In recent years, public colleges have also seen state aid dwindling.