New York City’s 1.1 million public school students have permission to skip class to participate in the protests, but teachers have been barred from attending.

The demonstrations come before a climate summit at the United Nations next week.

Voices: Our Opinion section wants to share young people’s illustrations and videos with the world. Here’s how you can send them to us.

Related: A $155 million climate research project that begins today is attempting to measure how global warming will affect the Arctic.

Another angle: The number of birds in the U.S. and Canada has fallen by nearly 30 percent since 1970, scientists reported on Thursday. The loss of 2.9 billion birds is partly attributable to the loss of habitat and the wider use of pesticides.