Schools across Northern Ireland welcomed back thousands of pupils on Monday following five months of closure due to the Covid-19 pandemic.
Pupils in Primary 7, and Years 12 and 14 - whose preparation for exams was disrupted by the lockdown - and all vulnerable children returned to classes while all other pupils will begin the new school term from next Monday.
Three schools did not reopen following the detection of Covid-19 cases.
Ballyclare Secondary School will reopen on Tuesday following a deep clean and 72-hour incubation period while St Kevin's Primary School and St Louise's College, both on the Falls Road in west Belfast, also delayed their reopening following positive cases among the school community.
At Bloomfield Collegiate School in east Belfast, 240 students in Years 12 and 14 were back while the remainder of the 730 enrolment and 67 staff will follow in the coming days.
Principal Gary Greer said he was "reasonably anxious" ahead of reopening but delighted that the day had finally come.
"The girls are all very excited to be back and while there was a bit of nervousness around the new one-way system, but overall there's a very positive feel so far.
"I'm delighted with the way our staff have pulled together to ensure we're providing as safe an environment as we can," he said.
"I'm slightly more concerned about what happens in the family home as we have parents who are shielding and considered vulnerable so it's really about trying to reduce the risk for them."
However some teachers have expressed concern that schools have been 'rushed' into re-opening and without enough time to respond to new guidance, issued by Education Minister Peter Weir earlier this month.
It recommended the formation of protective bubbles for primary school children and pupils in years 8-10 in post-primary schools, while interactions between different year groups of older pupils should be limited.
While not mandatory for routine use by pupils, some schools have already said that they will be encouraging the wearing of face coverings when they return.
Jacquie White, General Secretary of the Ulster Teachers' Union, said the situation regarding protocols around Covid-19 in schools was still unclear.
"For a start, many of the measures schools undertook to get pupils back in the first place were based on plans to have 50% of children in schools at once.
"Now from next week all pupils should be back full time and we have only had limited time to assess exactly what that will mean," she said.
"Schools are finding that even some classrooms they had been going to use are no longer suitable given the numbers they're now expected to see.
"It's been an incredibly rushed and quick turn around, but it's not really until the children are back that we will see how it will work as that may well throw up other issues that we haven't even thought of yet."
Ms White added: "However, one of the most fundamental things we need clarity on is what should be done straight away if a child or staff member tests positive for Covid-19. We need a clear and robust plan, something like a flow chart, for instance, with step by step guidance on what to do, who needs to be isolated and how long they need to be out of school and so on."
Mr Weir, who visited St Joseph's Primary School in Carryduff, expressed confidence that appropriate safety measures have been put in place.
"The position that we've taken is in line with what is there from chief medical officers across the UK," he said.
"I appreciate that there are challenges and there will be problems out there bit it's trying to cope with those challenges and do the best that we can. I think all of us in the education system should be focused on the delivery of education for our young people."