An unpublished preliminary report commissioned by the Department of Education has shown no "drastic" irregularities in pupil-teacher ratios in public and private primary schools.
The survey of 120 schools, by Pricewaterhouse Coopers, was commissioned by the Department following claims in the late 1990s that one private school had inflated pupil numbers to get more funding for teachers.
The Labour Party education spokeswoman, Ms Jan O'Sullivan, has called on the Department to hold an investigation into the subsidising of private primary schools by the taxpayer.
Private schools should not be allowed to misrepresent their pupil numbers to get more funding, she said.
Ms O'Sullivan was responding to a report in the Sunday Business Post that Willow Park School, run by the Holy Ghost Fathers on the Blackrock College campus, Co Dublin, had overstated its pupil numbers for 25 years to receive more funding for its teachers.
The Department has confirmed that Willow Park, one of the most exclusive schools in the State, was investigated in the late 1990s after the Department discovered that pupil numbers were being misrepresented.
However, the new survey has shown that pupil-teacher ratios in private schools are now in line with recommendations.
The Department has also developed a scheme that is monitoring every child from junior infants through to secondary school. It will be able to track special needs funding for children, and pinpoint the time when a particular student leaves the system.
The survey was commissioned after the Department discovered it was funding more teachers than Willow Park was entitled to.
Private primary schools get State funding for teachers based on pupil numbers. Many parents choose to pay about €4,000 annually to send their children to private primary schools for two reasons: the social cachet and the lower pupil-teacher ratios.
The verdant playing fields and social advantage of Willow Park come from its status as a feeder school for Blackrock College.
The irregularities at the school came to light in the late 1990s. When the Department questioned Willow Park's stated pupil numbers, the school said it had ministerial permission for the practice, which had been going on for 25 years.
The Department could not find evidence of such permission and so agreed to fund only the complement of teachers required by pupil numbers.
"It's totally wrong that State schools in disadvantaged areas must operate only with the teacher numbers to which they're entitled, while private schools can manipulate the situation to get a better pupil-teacher ratio," Ms O'Sullivan said.