THE number of pupils in Northern Ireland's primary schools is at its highest in almost 20 years.

There are now 174,522 children in P1-7, the ninth successive year in which the total has increased.

With the education system at a "tipping point" financially, teachers fear the result will be even larger classes.

Unions have warned that many class sizes are already incompatible with modern teaching and learning practice.

Department of Education figures show pupil numbers continue to increase even though there are fewer primary schools year on year.

Data taken from the school enrolments census, which was conducted in October 2018, show 23 primary schools closed between 2014 and this year.

However, enrolments in P1-7 jumped by 800 pupils on last year. This is the highest number of primary school pupils recorded since 1999.

The increase is in line with a rise in children aged 4-10 in population estimates over the last five years.

In post-primary schools, enrolments also increased for the second year in a row to 142,237 pupils.

Similar to last year, there was an increase in non-grammar roll-calls - up by 1,700 - while grammar schools also had slightly more pupils.

A recent audit report into the financial health of schools highlighted pressure on budgets, increasing pupil numbers and sustainability issues.

It warned action needed to be taken "as a matter of urgency".

About 90 per cent of schools' budgets are spent on staff and the audit office warned that reducing teaching numbers may lead to increases in class sizes and a reduction in subjects offered.

The Ulster Teachers' Union said large classes are short-changing children and putting "intolerable burdens on teachers".

General secretary Avril Hall Callaghan said the biggest single influence on the education system is class size.

Countries including Finland and Sweden that top education rankings, she said, operate with much smaller classes.

"Smaller class sizes have been shown to bring clear educational benefits for pupils. Children can have more one-to-one time with the teacher with all the benefits that brings in terms of improved pupil behaviour, educational performance and attainment," she said.

"Teachers are already coping with growing numbers of children with increasingly complex learning and behavioural needs who might formerly have been educated in the special school sector.

"Now class sizes look set to jump again. As always it will be the teachers, and ultimately the children, who will pay the price."

The statistics also revealed there are now approximately 100,000 pupils in all schools who are entitled to free school meals - about three in every 10.