An unexpected email put Cortni Marie Nucklos, a teenager from a poor South Carolina family, on the fast track to Harvard University. She is among a lucky few that Harvard and its elite college rivals are struggling to increase.

Two years ago, Nuckloss sole source of support was her mother, a textile-mill equipment operator earning less than $30,000 a year. Harvard wasnt on the now 18-year-olds mind until she got an unsolicited invitation to a recruiting session. Her mother drove her 50 miles to hear about free tuition offered by the Cambridge, Massachusetts, college, Americas oldest, richest and most elite.

Harvard is dispatching recruiters to depressed US locales, courting low-income applicants to help diversify the 6,715 undergraduates who are mostly from well-off families. Harvard, Yale University and other Ivy League schools say they arent attracting as many disadvantaged students as they want, even with offers of free tuition. Nucklos was persuaded to apply when recruiters said financial aid would cover almost all of Harvards $47,215 in annual costs, including room and board. It was so influential, she said. It was actually cheaper for me to go to Harvard than to go to a state school where I live.

Harvard in December revised aid plans to become more affordable to the middle class, adding to its existing policy of free tuition for students from families with annual incomes below $60,000. Less well-known is Harvards recruiting campaign among poor families aimed at preventing the school from becoming an exclusive preserve of the rich.

 What were trying to do is get these missing people into the game, said William Fitzsimmons, 64, dean of undergraduate admissions. They need a chance to compete against the affluent. Just 12% of Harvard undergraduates receive Pell Grants, a form of aid for households with income below about $40,000. More than 40% of US families are in that category, according to the Census Bureau.

Academic achievement is highly correlated to income levels, and that isnt something these institutions can change on their own, said Sandy Baum, 56, an economics professor at Skidmore College in Saratoga Springs, New York. About a decade ago, Harvard recognised the need to seek students from low- and middle-income families, with the aim of maximising opportunity for Americans. The school also faces the threat of legislation to force it to spend more of its $34.9 billion endowment on student aid.

Senator Charles Grassley, the Iowa Republican, has said college needs to be made more affordable. He has also raised issues of tax fairness in connection with Harvards investment pool and those at other wealthy colleges. A Massachusetts legislator last week proposed taxing endowments of Harvard, Massachusetts Institute of Technology, Amherst College and other wealthy private schools to help plug the states budget gap.

If they limit their enrolments to wealthy students they are basically enriching the rich and impoverishing the poor, said Thomas Mortenson, 65, senior scholar for the Washington- based Pell Institute for the Study of Opportunity in Higher Education.

They ought to be free to do whatever they want to do, but I dont think they deserve tax-exempt status if they are weakening and dividing the country. In an initiative begun in 2004, Harvard buys lists of high school students who excelled on standard tests. The school focuses on regions where US Census Bureau data show that incomes are below the US average. Harvard locates the students and sends recruiters to meet them.

While Harvard says it wants to have students from low-income families represent a larger proportion of the college, the campaign has helped increase the number of students who receive Pell Grant faster than leading rivals such as Princeton University. Harvards Fitzsimmons said the school doesnt have a quota it is trying to meet.

In the last academic year, Harvard had 808 Pell recipients, twice as many as a decade earlier, according to US Department of Education figures, better than many schools. The number of students getting Pell Grants at Yale fell 29% in the past 10 years, causing the school to institute programs similar to Harvards.

The emphasis used to be on recruiting minorities to the school and Yales last incoming freshman class was 30% students of colour, said Jeffrey Brenzel, dean of undergraduate admissions since 2005. The focus toward socio-economic diversity didnt gain as much attention until about three years ago, he said.

We have broadened our recruiting efforts and improved financial aid to address socio-economic class and low-income access as well as race, said Brenzel in an email. These efforts take time.

Over the past decade Pell grantees fell 33% at the University of Pennsylvania in Philadelphia; and 21% at Cornell University in Ithaca, New York, according to the Education Department. The reason for the decline in Pell recipients at Penn may be that potential applicants are put off by the schools cost, now $46,124 a year, said William Schilling, director of student financial services. Cornell spokesman Simeon Moss said he was unable to explain the drop in Pell recipients.