The criteria used for the allocation of teachers to primary schools is published annually on the website of the Department of Education and Skills. The key factor for determining the level of staffing resources provided at individual school level is the staffing schedule for the relevant school year and pupil enrolments on the previous 30 September.
Staffing arrangements for the 2017/18 school year are set out in circular 0017/2017 which is available on my Departments website.
The staffing arrangements include an appeals mechanism for schools to submit an appeal under certain criteria to an independent Appeals Board.
The school referred to by the Deputy had an enrolment of 501 on 30th September 2016. This allows for a mainstream staffing of 18 classroom teachers for the 2017/18 school year.