Pupils who begin a phased return to secondary school later this month could face two-metre social distancing rules.
A Scottish government advisory group says the “additional protective measure” should also apply on school buses.
The two-metre rule is already in place for teachers at secondary schools, while primary pupils should observe it “whenever possible”.
Scotland’s youngest pupils are likely to return full-time from 22 February.
Some senior secondary pupils preparing for exams could also be back in the classroom from the same date.
The tougher new social distancing guidelines have been put forward by the government’s advisory group on education and children’s issues.
Education Secretary John Swinney described the proposals as “an important scientific and clinical update”.
They are in addition to advice that there should be two-metre distancing between adults not from the same household within primary schools.
Lateral flow testing kits will also be offered to:
The government advice calls for “a combination of approaches that prevent crowding” within schools.
These include classroom distancing and staggered start times “especially in older age groups”.
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 masks when moving about within the school and on school buses.
The first children back in school on 22 February are expected to be all pupils in P1-P3 as well as pre-school children.
There will also be a part-time return, but on a very limited basis, for senior secondary pupils to allow them to complete work for national qualifications.
Only between 5% and 8% of a secondary school’s pupil roll will be able to be present at any one time.
First Minister Nicola Sturgeon has stressed that the reopening of schools was dependent on the continued suppression of coronavirus.