Hundreds of young people have missed a day of school in order to protest against what they say is one of the greatest threats to their future.
Primary and secondary school pupils descended on the Senedd in Cardiff Bay on Friday, taking part in the global Youth Strike 4 Climate.
Protest organiser Beth Irving, 17, said schools should recognise the importance of climate change as an issue.
"We are struggling to keep up with an ecological crisis," she told BBC Wales.
The Welsh Government said it wanted all young people to be "ethical, informed and valued members of society".
Meanwhile, Downing street has criticised school children taking part in the protests, saying the disruption "increases teachers' workloads and wastes lesson time".
Beth is part of a much wider global movement, known as Schools 4 Climate Action.
It began with 15-year-old Swede Greta Thunberg skipping class to sit outside government buildings in September, accusing her country of not following the Paris Climate Agreement.
Since then, tens of thousands of children across Belgium, Germany, Sweden, Switzerland and Australia have been inspired to hold their own demonstrations.
And now, for the first time, a coordinated protest is happening across the UK, with pupils taking to the streets in more than 30 cities and towns.
"I appreciate education is important, but one day of my education - if this has the impact we want it to have - will be so much more powerful and in five, 10, 20 years' time, if I have a university degree it will be worth nothing if it is under water," added Beth, who studies at Atlantic College, in St Donats.
"Our education system is not addressing climate change as a crisis, it brushes over some details and tells you 'this is happening by the way', but doesn't go into the severity."
Schoolchildren from Carmarthenshire also travelled to the capital where they joined forces with local pupils.
Madi Wood-Gilfoyle, 15, from Carmarthen, said: "It's my first protest, I didn't know what to expect, it feels a bit scary. But it's nice to know we can make a difference.
"It's going to be annoying to copy up work. Teachers might be angry but in the end that's small compared to the world."
Kieran Ellis, 17, also from Atlantic College, said "the fate of the world" was more important than missing a day of classes, which he said he could catch up on.
"It is my first protest. It is really exciting," he said.
"We have been left with other people's mess to clean up. We are at the point of no return now."
Radnor Primary School was one of the few primary schools in attendance.
Teacher Eoghan Walsh, who runs the after-school Eco-club, said he felt it was part of his responsibility to tell the children about the strike, adding that parents had been asked for permission.
"The children have really bought into it. We have won awards for promoting cycling, we petition businesses to reduce plastic and have a green flag status," Mr Walsh said.
Paddy Corrigan, 11, of Albert Primary School in Penarth, said: "I wanted to support the battle. It is a huge problem and we need to act before many animals are extinct in the future."
And 13-year-old Lilly Rose, of Stanwell School in Penarth, added: "It's very important for everyone to be aware of the issue. It's going to affect our future. I hope we can make a difference."