The government admits the evidence for using masks in schools to reduce spread of Covid is “not conclusive”.
The uncertainty is acknowledged in a review used by ministers in England to make their decision to introduce face coverings in classrooms.
The government’s own study in the autumn did not provide proof of a statistically significant impact.
The evidence review says other studies have provided mixed results, but taken together suggest they may help.
And the move was backed by the UK Health Security Agency.
The review has only just been published following the announcement on Monday about the return of face coverings in classrooms.