All secondary school pupils could be required to wear face coverings in the classroom as well as corridors when they return to school later this month.
Currently only S4 to S6 pupils are asked to wear masks in classrooms.
But a Scottish government advisory group says this should be extended to pupils in S1 to S3 when the phased return begins from 15 March.
The Scottish government said it would publish updated safety guidance next week.
The advisory group on education is also recommending that while two-metre distancing should remain in school buildings, it can be cut to one metre on school transport and relaxed in general during outdoor learning and activities.
The advice from the group says: "The sub-group published updated advice on 12 February on the mitigations required to ensure a safe return to in-person learning for staff and pupils.
"That advice remains relevant and has been strengthened in one area to require face coverings to be worn throughout the day by all secondary aged pupils (not just senior phase)."
Members of the groups also welcomed the plan for lateral flow testing to be in place for all school staff and senior pupils as part of the phased return
The advisory note adds: "There may be value in extending this approach to all secondary age pupils, in some circumstances, for example in areas of higher prevalence."
Scotland's youngest primary pupils returned to school on 22 February., with years P4 to P7 returning to classrooms full time from 15 March.
Covid restriction rules introduced for schools last October meant senior pupils and their teachers had to wear face coverings in classrooms.
Prior to that, secondary pupils and staff only had to wear face coverings when moving about within the school and on school buses.
They were encouraged to social distance "where possible", but there were no formal distancing rules for pupils.
One-way systems were introduced in corridors and physical contact including hugging and high-fiving was ruled out.
Schools across Scotland have been closed to the vast majority of pupils since the Christmas holidays, with learning being done at home and online.