Schools are safe places for children and staff, Northern Ireland's chief medical officer has said.
Professor Sir Michael McBride made the comments in a detailed letter about schools to pupils, parents and staff.
He added, though, that it was "inevitable" there would be Covid cases in schools.
But he said there was a "certainty of long-term harm to many children and young people" from not attending school.
"The public health grounds for keeping and supporting children at school are extremely strong," he wrote.
His letter comes as the Public Health Authority (PHA) takes over responsibility for contact tracing in schools on Friday.
In his letter Sir Michael said that the Covid pandemic had damaged children's wellbeing, mental health and education.
"Children from more disadvantaged backgrounds have been particularly negatively impacted," he said.
"As we progress through the pandemic response, we must continue to strike a balance between safeguarding children's education and wellbeing and measures to contain Covid."
Sir Michael said that now was the right time to take a more targeted approach to contact tracing in schools and said he was writing to explain why that was the case.
"Multiple sources of evidence show that a lack of schooling increases inequalities, reduces the life chances of children and can exacerbate physical and mental health issues," he said.
"School improves health, learning, socialisation and opportunities throughout childhood, adolescence and into adulthood."
He wrote that it was "no longer necessary" to close schools as had happened earlier in the pandemic.
He also cited large-scale studies from England and Scotland which showed "the vast majority of those identified as school close contacts and sent home to isolate during the last academic year did not go on to develop Covid".
The chief medical officer said that the overall risk of children becoming severely ill from Covid was extremely low.
He also said all school staff had the chance to be fully vaccinated, and that many other safety measures remained in place in schools.
"It is my professional opinion, which is shared by my chief medical officer colleagues across the UK, that very few, if any, children or teenagers will come to long-term harm from Covid due solely to attending school," he said.
"This has to be set against a certainty of long-term harm to many children and young people from not attending school."
Sir Michael said the contact tracing taken on by the PHA would bring Northern Ireland into line with England, Scotland and Wales and identify children with the "closest contact" to a positive case.
He also said it would free principals and teachers to get back to "doing what they do best - teaching and inspiring our children and young people."