Mr Johnson said: “When we begin to move out of lockdown I promise that [schools] will be the very first things to reopen.
“That moment may come after the February half term although we should remain extremely cautious about the timetable ahead.
“As was the case last spring, our emergence from the lockdown cocoon will not be a big bang but a gentle unravelling.”
The Education Secretary Gavin Williamson will also explain the Government’s U-turn over school closures and exam cancellations.
The PM insisted that schools were safe and told the Commons: “All the evidence shows that schools are safe and that the risk posed to children by coronavirus is vanishingly small.
“For most children the most dangerous part of going to school, even in the midst of a global pandemic, remains I’m afraid crossing the road in order to get there.”
Mr Johnson said it would not be “possible or fair” for all exams to go ahead this summer as normal.
He said they had done “everything in our power” to keep schools open and every course of action was taken.
However, he described schools as a “vector or a potential vector” for spreading the virus between households.
The House of Commons has been recalled from the Christmas recess to retrospectively vote on the measures which came into force today.
The PM is not expected to face a significant Tory rebellion on the scale seen over the November lockdown and Labour has said it will back the new lockdown.