A growing recognition that even families earning between $100,000 and $200,000 are struggling to pay for college prompted some wealthy universities and colleges to dig deeper into their sizeable endowments and offer scholarships and grants once reserved for lower income students.

But the move has also sparked debate, particularly among groups that argue any increase in scholarships should benefit the neediest students, who otherwise would be shut out of higher education.

Following decisions over the years by Princeton University and a handful of small select schools, such as Amherst and Williams colleges, to offer more financial assistance to middle-income students and replace loans with scholarships, Harvard and Yale made similar announcements in the last month and a half. Harvard and Yale, the country's two wealthiest universities, both said they would increase their financial aid budgets by more than $20 million next year.

Harvard, with an endowment of $34.6 billion, will allow families earning between $120,000 and $180,000 a year to pay just 10 percent of their income toward their child's college costs. At Yale, which has a $22.5-billion endowment, families earning between $60,000 and $120,000 will pay from 1 percent to 10 percent of Yale's $45,000 annual costs.

Both Harvard and Yale said that students from families earning less than $60,000 will pay nothing.

Since then, other schools with healthy endowments, including Duke University, have made similar decisions. On Tuesday, Dartmouth College announced that students with family incomes of $75,000 or less will receive free tuition - $35,000 of the total cost of $45,000 - and student loans will be replaced with scholarships.

The Ivy League college cited census data that shows 70 percent of U.S. households earn less than $75,000 a year, and the median family income is $46,326.

Virtually all of the universities and colleges expanding their aid offerings are in a select tier - schools with endowments of more than $500 million or $1 billion. Brown's $2.3-billion endowment ranks 26th nationally.

The rest of the state's colleges and universities rank far lower, and none come close to the half-billion mark. Several of these colleges offer merit-based aid to attract competitive middle-income students to their schools, a practice also called "tuition discounting."

In recent years, Providence College has moved to reduce merit-based aid while increasing scholarships for needy students, in an effort to lure more low-income and first-generation students.

The Dominican college, with an endowment of $136 million, is unable to offer upper-middle-income students as much scholarship money as wealthy Ivy League universities are now doing, said Christopher Lydon, who heads PC's admissions and financial aid division.

"We are not in a position, endowment-wise, to answer every move other colleges make," Lydon said.

Critics of the expansion of financial aid dollars to middle-income students warn that it could take money away from needier students.