The best guess is that one and half million students, in over 120 countries, struck on Friday 15 March to demand that their governments start emergency action on climate change.
In London, the central rally of school students in Parliament Square was 4,000 or more. Everyone we talked with said there was no ongoing organisation in their school for the walkout. They’d found out about it on social media and come with their friends.
There were also sizeable groups of university students at Parliament Square.