Around 107,000 primary school children are being educated in classes of 30 pupils or more, according to data released today by the Department of Education.
Figures posted on the Department website relating to last year show that class sizes have grown considerably as a result of cuts in teacher numbers in Budget 2008.
The figure for the previous year was under 100,000.
Most of those children are in classes of 30 to 34 children. However, around 8,000 children are in classes with 35 pupils or more.
The schools worst effected are those in developing areas, such as the country's commuter belts.
Primary teacher's union the INTO said the figures show how children are paying the price for economic mismanagement.
It said billions of euro is being spent to keep Anglo Irish Bank on a life support machine but children are losing out.