Private schools have warned of the dangers of using a "statistical formula" to judge the abilities of university applicants.
Individual candidates should be chosen on their own merits, avoiding a "crude" form of positive discrimination, according to the Independent Schools Council (ISC).
The warning comes after a government task force said academics needed to look at more than candidates' predicted A-level grades as an indicator of possible performance at degree level.
Its suggestions include more scrutiny of GCSE results, allocating places for a certain percentage of top-performing pupils and students sitting US-style aptitude tests.
'We are doing the same'
ISC spokesman Dick Davison said: "Independent schools fully support efforts to identify talented youngsters, whatever their background or previous education.
"They are engaged in the same process themselves.
"They believe, however, that at the university level, that objective must be achieved through more open and transparent university admissions policies, applied after students have received their A-level results, not before."
Earlier this year, independent schools complained of "positive discrimination" by Bristol University, which they said would disadvantage their pupils unfairly.
Their representative body - the Headmasters' and Headmistress' Conference (HMC) - called for a boycott of the institution, which was later withdrawn.
Bristol has denied allegations of positive discrimination.
Mr Davison added: "What all good schools would dispute is the idea that a statistical formula - whether based on the social background of
students or the standards achieved by their schools - will achieve a
fairer distribution of university places than a full and proper
consideration of individuals' achievement and potential."