England’s schools will find out later how the government plans to relax rules that has caused large number of pupils being sent home if a child in close contact with others receives a positive Covid test.
Last week the “bubble” system saw more than 375,000 children sent home.
Boris Johnson said Education Secretary Gavin Williamson would outline a move away from sending “bubbles” home but move to testing instead.
There has been widespread concern that thousands of pupils are missing school unnecessarily.
Last month the number sent home from school for Covid-related reasons quadrupled – but only about 4% were from confirmed cases.
Mr Williamson is expected to say the changes will come into effect on 19 July, alongside the lifting of other Covid restrictions.
The PM’s message on Monday was it was “now or never” to lift the restrictions.