Pupils and staff will have to wear face coverings when moving around secondary schools from Monday.
The rule will also apply on school transport for primary school pupils aged five and above and all those at secondary school, but not in classrooms.
It comes as restrictions ease in other areas of life, with gyms, swimming pools and indoor sports courts allowed to reopen from August 31.
Announcing the new rules for schools last week, the Scottish Government said while staff and students can continue to wear face coverings if they wish, they will not generally be necessary in the classroom as there is greater scope for physical distancing and face coverings can have an impact on learning and teaching.
However, it remains the case that where adults cannot keep a two-metre distance and are interacting face-to-face for more than 15 minutes, face coverings should be worn.
Education Secretary John Swinney said: “There is increasing evidence that face coverings can provide some protection for the wearer as well as those around them.
“We also know that some pupils have found it very difficult to physically distance when moving around school, which could increase the risk of transmission of the virus.
“And on school transport, as on public transport, there can be mixing between different age groups.”
He added: “We want to continue to protect what we have achieved in suppressing the virus and re-opening schools, and to do the best for children in schools.”
Mr Swinney has stressed pupils will not be excluded from school if they do not wear a face covering.
It comes following advice from the World Health Organisation that children aged 12 and over should wear face masks.
From Monday gyms, swimming pools and indoor sports courts can reopen, subject to guidance.
This is two weeks earlier than the previous date of September 14 which had been pencilled in.
Indoor activities for children are also now allowed.