Today as part of a global movement - inspired by the 16-year-old Swedish activist Greta Thunberg - Scottish pupils will take to the streets to demand action to tackle climate change.

Now the Educational Institute of Scotland (EIS), the country’s largest teaching union, has joined Scotland’s children’s commissioner, Bruce Adamson, in calling for the pupils “not to be sanctioned or punished as a consequence”.

In an open letter to education leaders published earlier this week, Mr Adamson expressed concern that some pupils had been “threatened with detention or other punishment” for taking part in the 20-27 September global climate strike, timed to coincide with an emergency United Nations climate summit.

‘Read this and cry’: Anger over textbook showing climate change ‘positives’

Related: Sturgeon ‘heartened’ by pupils striking over climate

Action: 8 things schools can do to tackle the climate crisis

Colleges: Climate strike college students ‘could lose bursaries’

First minister Nicola Sturgeon last week lent her support to young people who will miss school to protest against the global climate crisis, in response to concerns that pupils in Edinburgh could face police action for joining the global climate strike today.

Now, in a letter sent to all 32 Scottish local authorities, EIS general secretary Larry Flanagan has also come out in support of the pupils.

He said: “If we are to encourage our pupils to be confident individuals that effectively contribute to society on global themes including sustainability, we shouldn’t seek to punish them when they campaign for global sustainability.”

Mr Flanagan, however, said that teachers ultimately had to follow their employer’s advice for dealing with unauthorised absences, but he called for a common sense approach from authorities.

He added: “We believe this should be founded on the basic premise that for pupils who are 16 or over, any decision to participate in the strike can be made on an independent basis and then processed in line with the local authority’s policy. For those under 16, pupils should be advised that they should seek parental endorsement if they are going to be absent and that parents should inform the school.”

Organisers expect thousands of marchers to descend on Edinburgh today with other climate strikes taking place in Glasgow, Dundee, Aberdeen and elsewhere.