NEW YORK - IN WHAT may be a happy surprise for thousands of high-school seniors, Harvard plans to admit 150 to 175 students from its waiting list, while Princeton and the University of Pennsylvania expect to take in 90 each.

Their decision is creating a ripple effect, with other highly selective universities going deeper into their waiting lists as well.

'This year has been less predictable than any recent year,' said Mr Eric Kaplan, interim dean of admissions at Pennsylvania.

'We all need to fill our classes and replace students who have been taken off waiting lists at other institutions. The waiting-list activity could extend for a significant time.'

Although universities turn to waiting lists to fill their classes, it is unusual for the most selective ones to go so deep, university officials say.

The waiting lists this year have been unusually long as a result of new acceptance and financial-aid policies, and a record number of applications.

Harvard and Princeton eliminated early admission for this year, forcing more students into the regular pool of applicants.

As a result, the Massachusetts Institute of Technology and other schools lengthened their waiting lists, hedging against the possibility that the students they accepted would take up offers from competitors such as Harvard University.

Right up until the May1 deadline for students to respond to admission offers, universities had been unsure of what to expect.

Yale and Princeton universities and the Amherst College were among top-

ranked US schools that increased - by as much as 50 per cent to 90 per cent - the number of students told they could be accepted if other students pulled out.

Yale, for instance, put 1,052 students on hold, up 22 per cent from last year, while Princeton placed 1,526 on its waiting list, up 93 per cent over last year.

Harvard would not confirm the plans for its waiting list.

In an e-mail message sent on Thursday to colleagues at dozens of other institutions, Mr William Fitzsimmons, Harvard University dean of admissions, said: 'Harvard will admit somewhere in the range of 150 to 175 from the waiting list, possibly more depending on late May1 returns and other waiting list activity.'

A Harvard spokesman said the university had accepted fewer students this year to avoid overcrowding the freshman class.

Yale dean of admissions Jeffrey Brenzel said there would be about 45 offers this week for those on the waiting list, and probably another round later this month.

Even universities that had more than filled their freshman classes were wondering about how many would pull out if admitted from waiting lists elsewhere.

'We are over target right now, so we are in good shape,' said Stanford dean of admissions Rick Shaw.

'But I am keeping a small group on the waiting list because I think there will be some impact on waiting-list activity at other schools.'

Mr Tom Parker, dean of admissions and financial aid at Amherst College in Massachusetts, said: 'It really kind of blows our procedure for the waiting list out of the water.'

Amherst placed 1,400 students on its waiting list, up 40 per cent from a year ago, to help fill a class of 440, he said.

NEW YORK TIMES, BLOOMBERG