Students attending private schools are three times more likely to go to some of the country's most prestigious universities.
The latest school League Tables in today's Sunday Independent show that less than 10% of all students who sit the Leaving Cert attend a fee-paying school.
However, last year, 30% of new entrants to Trinity College Dublin all came from fee-paying schools.
At UCD, 28% of incoming first years came from a private school.
The data also shows that students in Dublin, Cork, Limerick and Galway are more likely to stay within their own county to study at third level.
More than 90% of those from Dublin stay in the capital to study, while UCC and CIT account for 78% of all Cork students who go on to third level.
Almost three-quarters of Galways students attend NUIG or GMIT and two-thirds of Leaving Cert pupils in Limerick go on to UL or LIT.
In the south-east, more than half of sixth year students progressed to WIT while 23% of their Kilkenny counterparts also attended the Waterford Institute.
In Donegal, 43% of students stayed in the county and studied at Letterkenny IT while IT Kerry took in almost a quarter of Kerry students.
That figure is the same in Kildare where 24% of students study at Maynooth University.
Athlone IT is the most popular for people from Westmeath, Offaly and Longford.
Louth pupils account for 23% staying within the county to study at Dundalk IT.
Reporting by Trevor Keegan