Thousands of pupils are swapping pens for placards as the student climate protests sweeping Europe reach the UK.
Demonstrations are taking place this Friday lunchtime in more than a dozen towns and cities across the country.
Organisers UK Student Climate Network says it is their first nationwide protest aimed at averting "the impending climate breakdown".
The movement has been inspired by Swedish student Greta Thunberg, who has been skipping classes every Friday to protest about climate change in front of the Swedish parliament.
Other students protests have been held in Belgium, the Netherlands, Germany and Switzerland in recent weeks.
"We’ve seen the last few decades go by, characterised by missed opportunities, and a lack of leadership on climate action," said Anna Taylor, from the UK Student Climate Network.
"We’re running out of time for meaningful change, and that’s why we’re seeing young people around the world rising up to hold their governments to account on their dismal climate records.
"Unless we take positive action, the future's looking bleak for those of us that have grown up in an era defined by climate change.
"We’ve had enough and we’re making sure our voice is heard.
"We’re ready to let politicians know we won’t accept anything less than a commitment to protect the planet for the good of everyone.
"We have a clear message for Theresa May: do not let the big polluters steal our future”.
"We do not condone children and young people missing school as a consequence of supporting action," said the National Association of Head Teachers
"Children should only be out of school in exceptional circumstances. Whilst NAHT supports the right of young people to express themselves, first and foremost, pupils should be in school during term time.
"Nothing is more important than a child’s education and there are plenty of ways that children and young people can engage with social issues in school.
"While a school leader’s role is to ensure children attend school, are kept safe and receive a good quality of education, it is right that individual school leaders can decide how best to respond to any proposed protest by students in their school on Friday."