Around €48m will be spent on renting school prefabs this year.
The figures were revealed in a Dáil reply to Fine Gael's Education Spokesperson Brian Hayes.
The data shows that nearly 200 schools around the country are paying around €50,000 a year to rent prefabs.
The Department of Education says a review of rental policy is underway and value for money is a central aim.
But Brian Hayes said it is a scandalous waste of money and an insult to children, parents and teachers who are seeking new school buildings.