Pupils have been threatened with detention if they skip class to take part in a climate change protest tomorrow.

Hundreds of young environmentalists are expected to go on "strike" as they march through Canterbury city centre, with many schools across the district allowing students to miss lessons to take part.

But Barton Court Grammar School has told its pupils it does not support the Youth Strike 4 Climate event and any absence from class will be "unauthorised".

Sixth form students say they have even been told they face detention if they defy the school's orders.

Barton Court told parents: "The school are not supporting this event. We expect all students to be in school and any non-attendance will be unauthorised."

Department for Education guidance allows head teachers to approve some absences, but only in "exceptional circumstances."

The protest is one of dozens across the country and is expected to draw huge crowds of young people - from primary school age to university students - urging the government to take action on global warming.

Demonstrators will gather at the St George's Clocktower at 10am and then march through the city centre, finishing at the bandstand at Dane John Gardens.

Simon Langton Grammar School for Boys is allowing its pupils to take part on the proviso they have permission from their parents and write a letter showing an "understanding of the issues involved".

Head of school Ken Moffat says about 60 pupils are planning to attend.

"I'm delighted that students are making a public statement that has drawn attention from the media," he continued.

"It will be their world and I understand that they are angry that there is no co-ordinated international governmental policy that is effective in combatting climate change or human damage to our planet.

"The younger generation is teaching the older generation valuable lessons that they have failed to learn. My generation has made a cock up of the economy, blundered into Brexit, allowed the rise of politicians like Trump and neglected the planet.

"If I was 14, I'd be very, very angry."

The day of action has been inspired by 16-year-old Swedish schoolgirl Greta Thunberg, who hit global headlines after she held a solo protest outside her country's parliament every Friday last summer.

Youth Strike 4 Climate protests have been confirmed in more than 50 towns and cities across the UK, and the "day of action" is expected to be the biggest demonstration by young people since the tuition fee hikes in 2010.

Barton Court did not respond to numerous requests for a comment.