Thousands of students in Belgium have skipped school for the third week in a row and more than 30,000 swamped the centre of Brussels to demand better protection of the world's climate.
What started out as a march of a few thousand high school students has swelled to a vocal movement that also included many that skipped courses at university.
Brussels police estimated the crowds that braved the cold and snowy conditions at 32,000.
Another climate march - adults included - is set for Sunday.
It drew some 70,000 people last month.
"The planet can do without us, but we cannot do without the planet," was one of the many signs carried around.
Chants of "Youth for climate" were heard around the centre of Brussels and the din of youngsters was reminiscent of fans cheering a football victory.
After some 3,000 demonstrators took part two weeks ago, the rally ballooned to 12,500 last week and nearly tripled in size this time.
16-year-old student Kate Merhy said:
Many schools have been lenient towards those skipping classes, with several demanding selfies during the march as proof that their no-shows had good cause.
This time, even some grandparents came to support the children.
"We want to show our solidarity with our grandchildren who are so numerous here, and honour those who are trying to do something," said Michel Depaepe, a grandparent of one of the demonstrators.
- Press Association