More than 100,000 working days were lost due to teacher sickness absences in the most recent financial year, according to new figures.
Over the same period, non-teaching staff sickness absences accounted for over 450,000 working days lost.
Figures from the Department of Education also show the impact the pandemic had on teaching sickness rates. Despite schools being closed during lockdown periods in 2020/21, teaching staff sickness absences accounted for 105,343 working days lost, compared to the previous year's figure of 150,299.
Similarly, for non-teaching staff, absences fell from 560,464 working days lost to 452,657 in 2020/21.
In the last five years, 710,137 working days were lost due to teaching staff sickness absences, and 2,655,617 working days were lost due to non-teaching staff sickness absences.
Ulster Unionist MLA Andy Allen said these "shocking" figures highlight the growing pressure our teachers and educational support staff are under in managing an education system that is "not fit for purpose".
"There is an ongoing discussion regarding the need to redesign our education system and how it's delivered, a system where the financial waste created by duplication is causing a serious impact on the delivery of quality education to many of our children," he said.
"What often goes without comment is the impact the pressures this systemic failure places on education staff, our teachers and education support staff who are pressed to do more and more, with little or no consideration given to the impact this growing demand has on their physical and mental wellbeing.
"We need to start now to make our education system fit for purpose, as much for the staff as for the pupils. I would expect any new Assembly to place redesigning our education system at the heart of the next mandate. Until then, I call on the current Education Minister to do everything in her power to support fully the staff in every school and educational facility."
The Department said it “monitors absence levels in the education sector closely to seek to ensure that absence levels are kept as low as possible and managed effectively. DE officials have been working with employing authorities to develop and implement a Managing Attendance Strategy for the Education Sector”.
“This commits employers to seek improved attendance levels across the Education Sector through the proactive management of health and wellbeing and provision of support for those who are ill. Effective management of absence will also be implemented using agreed sickness absence procedures and the development of systems and information.”
The news comes after Education Minister Michelle McIlveen was urged in October to advise schools on the steps they need to take when schools cannot be staffed properly due to Covid.
Some schools are having to send pupils home because there are no teachers available to teach them, the Northern Ireland Teachers’ Council (NITC) said.
Secretary of the NITC and NASUWT national official for Northern Ireland, Justin McCamphill, said there was growing concern that high levels of Covid cases and better better pay and conditions offered elsewhere are contributing to staff shortages.
“NITC is alarmed that the levels of Covid in schools have contributed significantly to schools being unable to source enough substitute teachers,” he said.
“This is not the only contributing factor, many newly qualified teachers have sought work outside of Northern Ireland, where there is better pay and conditions of employment.”