16.5% of primary school pupils in North Tipperary are in class sizes of 30 or more while the figure for South Tipp is noticeably lower at 12%.
Figures from the Department of Education show Ireland still has the largest class sizes in Western Europe – with some primary school classes totalling 35 pupils.
The average class size in Tipperary is 23.7 pupils – up from 23.1 in the previous school year.
Nationally the average class size now stands at 24.8.
The Irish Primary Principal's Network says large class sizes impede the ability of teachers to cater to individual childrens learning abilities.
Brendan McCabe, President of the IPPN, says pupils benefit more when teachers can give them more time.