More than €6m has been spent on private school fees by the Department of Foreign Affairs over the past three years.
The 2020 bill, which covered annual tuition costs for 114 to 123 children of diplomats, came to €1.93m up until December last year.
In the two previous years, it exceeded €2m with €2.03m paid out in 2018 and another €2.09m in 2019.
The yearly cost per student works out at €17,000, officials records have revealed.
The Department declined to identify the location of the schools, saying it could compromise diplomats' safety.
It said it operates "in a complex environment. We have a fundamental duty of care to protect our staff and their families.
"There are a limited number of officers posted and children in school in each location and to provide a list of schools attended could jeopardise the safety of families and their right to privacy."
The €6m cost did not reflect the savings to the taxpayer from the children not attending Irish schools.
"It should be noted the costs set out do not factor in the considerable cost savings to the Department of Education in Ireland when places in Irish schools are vacated while the children of posted officers are living abroad," it added.
The department has previously provided estimates, stating savings were worth €6,200 for a primary school pupil and €8,200 for a student in secondary.
Other information shows the majority of private schools being paid by the department were in the major capitals of Europe and the Americas.
Annual costs have risen markedly from €1.63m in 2016 to an average of €2m a year.
This has been attributed to the changing demographic of staff posted abroad, many with younger families.
Such schools normally follow an international curriculum, allowing students to switch easily from one country to another if their parents are moved to a new posting in another country.
The first such school in Ireland opened in 2018 in the Leopardstown, Co Dublin.
Nord Anglia International School fees range from €11,130 for three- to five-year-olds up to €17,850 for older teens.