Pupils at private schools have received more offers of places at leading research universities this year than those at state schools, according to the Independent Schools Council's annual universities survey.
The survey of 139 schools shows a rise in the acceptance rate of Independent Schools Council (ISC) pupils at Russell Group universities to 65.6% this year from 62.5% in 2006.
But the Russell Group, which represents the largest research universities, said that it was working hard to ensure that it took pupils from state and private schools, and in some of its institutions the numbers of students entering from both were roughly equal.
Private school pupils applying for undergraduate studies are more likely to target the top universities. They are also far more likely to take sciences and languages and were more likely to apply to Russell Group universities than before.
The overall offer rate by the university admissions service, Ucas - where offers are made and taken up - for places at Russell Group universities is 13%.
The ISC survey, published today, shows that acceptance rates for independent school pupils are especially high (more than 80%) in biological sciences, physical sciences, mathematical and computer sciences, and technologies subjects.
According to the ISC, getting three A or B grades at A-level is the key to get a place at a leading universities and it is better to have three top A-level grades than the equivalent A-level points score made up from a larger number of less good results.
For instance, a pupil with three A-level A grades will get 360 points as will a pupil with one A and three C grades. But for many courses at leading universities three A-level A grades is the normal entry requirement, so lower grades with the same point score are unlikely to be accepted.
Jonathan Shephard, ISC chief executive, said: "These results show once again the superb job done by ISC schools in preparing pupils for entry to leading universities.
"Our research also shows that A-level point scores can be misleading as a measure of achievement: it is quality, not quantity, that counts."
According to the Russell Group's director general Dr Wendy Piatt, universities in the group were over-subscribed by high-performing candidates with an average of nearly eight applications per place.
Dr Piatt said: "One of the keys to successful applications to Russell Group universities is a strong academic record, and the facts show that pupils from independent and grammar schools have a good chance of gaining three As.
"However, admissions practices within the Russell Group universities also aim to identify potential in candidates over and above qualifications. Oxford, for example, has recently introduced a new admissions form offering schools the opportunity to provide detailed and reliable information about a candidate's educational environment. We are also exploring the ability of aptitude tests to identify potential which is not reflected in a candidate's academic record."
Dr Piatt added that several Russell Group universities have a broadly similar success rate for both independent and state school applicants. For example, at the University of Warwick the proportion of applicants who accepted a place they were offered from independent schools in 2006 was 10.5% compared to 11.0% from comprehensive schools.