Terry Hartle, senior vice president at the American Council on Education, said the strategy of raising both tuition and aid is risky, particularly with competition for students from wealthier backgrounds.

“That strategy only works as long as there are people willing to pay the full posted price,” he said.

Hartle said that tuition has outpaced inflation and family income for a generation, but that families have been generally willing to pay it. Sooner or later, he said, tuition will reach a point where that will change.

At Harvard, parents of incoming students who earn between $150,000 and $180,000 will now be required to pay just over 10 percent of their income. Previously, they had to pay ­between zero and 10 percent.

But Harvard is increasing subsidies for less affluent families, raising the ceiling for no contribution from $60,000 to $65,000. In all, the financial aid budget will increase $6 million over last year to $172 million.

“The total investment continues to grow,” said Jeff Neal, a university spokesman.

Northeastern University said it has increased aid to ­attract students from less affluent backgrounds with the goal of creating a “rich educational environment.” At the same time, the college must attract enough students who can pay full freight, now more than $53,000.