Principals and teachers say a better system is needed for contact tracing in schools.
Thousands of children are missing from school again this week as they are considered close contacts of someone with covid.
Children accounted for almost half of all Covid tests carried out last week.
Michael Gillespie from the Teachers Union of Ireland says they need to know how many of these tests are actually positive for the virus.
"Anybody could have seen that surge coming, the demand for testing in the first two weeks back with students returning to school with systems.
"What we're waiting for now is the results of those tests, they're going to come after 5 and 10 days and we'll see how the Delta variant is spreading.
"We're waiting to see how that testing turns into numbers."
