An additional 200 classes are needed for September to meet the demand for school places for children with special educational needs (SEN).
That is according to an internal letter sent to Education Authority (EA) staff that has been seen by BBC News NI.
The authority has asked for almost 90 of its workers in other jobs to volunteer to move to work in SEN support.
It cites staff shortages as the reason.
Restrictions on early years support for children during the Covid-19 pandemic is one reason for the "significant" rise in demand, according to the authority.
"This is at least partially attributable to a cohort of children who were less than a year old when Covid struck, now entering pre school," it said in the letter.
"Many of these children experienced limited early social contact, did not receive important child health surveillance contacts from health visitors and/or access to new-born health services.
