The Scottish Government announced the move following the latest scientific and public health advice, including World Health Organisation guidelines.
The Scottish Government said, unless exemptions apply, face coverings should now be worn in secondary schools, by adults and all pupils moving around the school in corridors and communal areas where physical distancing is difficult.
The ruling also applies to dedicated school transport by all children aged five and over, bringing it into line with guidance for public transport.
The announcement said staff and students can continue to wear face coverings if they wish to, but face coverings will not 'generally be necessary' in classrooms.
This is because there is greater scope for physical distancing and face coverings can have an impact on learning and teaching, it said.
However, it remains the case that where adults cannot keep a two-metre distance and are interacting face-to-face for a sustained period of 15 minutes or more, face coverings should be worn, it said.
Oban High School said it would notify parents and carers once it had received guidance from Argyll and Bute Council.
John Swinney, cabinet secretary for education, 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.
'We have worked with partners on the Education Recovery Group to update the guidance to ensure face coverings are worn in corridors and confined communal areas in secondary schools, and on school transport.
'Schools will be asked to ensure children and young people have clear instructions on how to put on, remove, and store face coverings. Any staff member or pupil will still be able to wear a face covering when they wish to do so.
'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.
'Alongside this change to the wearing of face coverings, we need to reinforce the importance of maintaining high standards of cleaning, personal hand and respiratory hygiene and physical distancing, where possible. In situations where there is a local cluster, use of face coverings throughout the day may be required.
'The position will be kept under review to ensure that our approach remains commensurate with the evidence and the levels of transmission in Scotland.'
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