Twenty prep school pupils received free schools meals last year – at a cost of £10,700 to the taxpayer.
The revelation has raised questions about increased uptake of free school meals at prep schools, where annual tuition fees cost over £2,600 in 2008/9 and have increased further following funding cuts.
Of 1,832 pupils enrolled in Northern Ireland's 15 prep schools in 2012/13, 20 got free school meals. The previous year there were 17 pupils receiving subsidised dinners.
Pupils are entitled to free meals if their family receives social benefits, such as Income Support or child tax credits. The annual cost of school meals per pupil is around £535.
The Department of Education could not explain the uptake. However, Sinn Fein West Tyrone MLA Michaela Boyle, who sits on the Assembly's education committee, said: "It could be that the parent of a child loses their employment – or some money has been left in a will."
Fellow committee member, South Down SDLP MLA Sean Rogers, said the subsidy was "alarming" when many low-income families didn't meet the threshold for free meals.