German Chancellor Angela Merkel has said she supports school students' protests about climate change.
It appears to contradict some education officials, who have criticised participants for skipping school and threatened them with exclusion.
Mrs Merkel said students might be frustrated at the time taken to move away from coal-based energy but asked them to understand it was a challenge.
Across the world, some students have been leaving school to demand action.
On Friday thousands of high school students in the city of Hamburg marched against climate change, with Swedish activist Greta Thunberg - who started the series of school strikes - present.
But the city's education official, Ties Rabe, wrote on Twitter: "No-one makes the world better by skipping school."
Meanwhile the education minister in the state of North Rhine-Westphalia has told schools that students face disciplinary action up to and including expulsion if they do not comply with their legal duty to go to school.
What did Merkel say?
In a video released on her official website, Angela Merkel said protecting the climate was a "challenge that people can only tackle together" (in German).
Asked about the Friday school strikes, which in Germany have been dubbed "Fridays for Future", Ms Merkel said the country's climate goals could only be reached with the support of wider society.
"So I very much welcome that young people, school students, demonstrate and tell us to do something fast about climate change," she said.
"I think it is a very good initiative," she added, without making reference to the fact that they were protesting during school hours.
But, she said, in her role she had to let them know that there were many steps to take before the full switch-off of coal, planned for Germany by 2038.
"From the students' point of view," Ms Merkel continued, "that may seem like a very long way away, but it will challenge us very much so I ask them to understand that too."
Two years ago a small survey suggested that Germans worried more about climate change than they did about terrorism.