I assume the Deputy is referring to primary schools.
The amount of grant paid to an individual primary school for capitation and ancillary services is determined by the school's enrolment, subject to a minimum grant for both capitation and ancillary services in respect of schools with enrolments up to 60, and a maximum ancillary services grant in the case of schools with enrolments of 500 or more.
Boards of Management have autonomy on how they use and prioritise this funding to meet their day to day running costs including for the provision of secretarial, caretaker and cleaning services.
The position therefore varies between schools and accordingly it is not possible to provide an estimated cost of employing a full-time secretary in each individual school.