More than 300,000 students returned to the classroom on Monday for the first time since before Christmas.
Primary school pupils from junior infants up to second class and sixth-year second-level students returned as part of a staggered resumption of in-person teaching.
Special schools also moved to full capacity after returning on a limited basis two weeks ago.
The Irish National Teachers Organisation (INTO), which represents teachers at primary level, said the first day back had “broadly been a success”.
“This is down to the hard work of school leaders and teachers, working with less than a week to adopt government guidance ahead of today’s reopening,” a spokesman for the INTO said.
“INTO will be keeping a close eye on primary schools as the week continues and we expect to meet with the Department of Education and education partners during the week.”
The INTO added that ahead of a wider reopening of primary schools, it will be monitoring schools’ mass testing reports from the Health Protection Surveillance Centre (HPSC) and “seeking up to date public health advice”.
“We will continue to press Government to roll out rapid antigen testing, ventilation monitors and to consider a mandatory face mask policy for older pupils to provide a critical defence from the virus and ensure our schools can remain open safely for the remainder of the school year,” the spokesman said.
Ronan Mac Grianna, a principal at Scoil Naomh Lorcan in Omeath, Co Louth, said his pupils were overjoyed to be back.
“When the children arrived, the vast majority of them literally ran up the hill to the school here. Our school is located on a hill overlooking Carlingford Lough here, and they just literally ran up,” he said.
“Everyone’s very happy, everyone’s delighted. It’s joy, even more so than relief. I’d say there’s a lot of relief among parents though.”
Mr Mac Grianna said: “For myself personally, the reason you go into teaching is for the human interaction every day. That face-to-face contact and communication and interaction, that’s a huge part of teaching.
“I definitely didn’t go into teaching to sit doing Zoom lessons all the time. It’s draining, it’s very difficult to know if you have full engagement with everybody.”
The Association of Secondary Teachers in Ireland (ASTI) said, having secured additional safety measures for the phased re-opening of schools, it would “continue to monitor the situation and engage with the Department of Education over the coming weeks”.
The Teachers’ Union of Ireland (TUI), which also represents post-primary teachers, said as the phased return to schools continued, “there is understandable anxiety among all in school communities, particularly given concerns around new strains of the virus”.
“Tracking and tracing measures must be robust and fit for purpose, while any member of the school community - staff or student - who has symptoms of Covid-19 or is a close contact of a confirmed case must stay at home,” said TUI general secretary Micheal Gillespie.
“We have already stated that we will not tolerate any slippage in terms of nonadherence to key safety measures in workplaces.”
Meanwhile, the Minister for Education Norma Foley has said antigen testing in schools had not been recommended by public health officials at this point. She said if this advice changed the Government would respond to that.
Ms Foley told RTÉ Radio’s Today with Claire Byrne show that the new variants had changed the circumstances but that younger children were still not being advised to wear masks and that this will also be kept under review.
An estimated 60,000 Leaving Cert students and 260,000 pupils in the earliest primary classes returned on Monday.
Third, fourth, fifth and sixth classes are due to return to primary school on March 15th along with fifth years at post-primary level. First, second, third and fourth-year students are due to return to secondary school on April 12th.
The reopening dates are provisional and may be delayed depending on whether the public health situation deteriorates. – Additional reporting PA