The CAO system is failing a large number of pupils and may need to be replaced by a broader entry system to third level, the Labour Party said last night.
The party's education spokesman, Mr Joe Costello, was responding to new figures, published in The Irish Times, which showed that students from private fee-paying schools were better represented at UCD and TCD than other students in 2000-2001.
Mr Costello said he had long supported the traditional CAO entry system, but if students from comfortable backgrounds were able to boost their performance through grinds, it might be time to undertake a review of how the CAO worked.
He said the new figures on first-year student admissions to UCD and Trinity College proved there was a "golden circle" in the education system from which lower- and middle-income families were excluded.
Mr Costello said the figures showed how recent cutbacks by the Department of Education were utterly wrong.
The ASTI said the publication of the figures, released under the Freedom of Information Act, should generate a debate about the education service.
Its general secretary, Mr Charlie Lennon, said there was a danger the statistics could be misused. "The fact is that these statistics tell us nothing about the performance of the schools concerned.They do not tell us whether fee-paying schools or grind schools could cope with pupils who are not selected by academic test or by ability to pay".
The Fine Gael spokeswoman on education, Ms Olwyn Enright, said the figures proved how wrong last week's cuts by the Department of Education were. "It is possible that location played some part in these figures, with students opting to attend the colleges closest to them. In many instances these choices are made for financial reasons, as students cannot afford the exorbitant rents charged to them," she said.