Thousands of schoolchildren across Australia skipped classes Friday to attend rallies demanding the government act on climate change.

But Resources Minister Matt Canavan said the students should be in school learning about science and mining, rather than discovering how to get on welfare.

The coordinated rallies Friday were held in close to 30 cities and towns and were inspired by a 15-year-old Swedish girl's activism.

In Sydney, more than 1,000 children, most in school uniforms, chanted slogans, while similar numbers blocked streets outside the Victoria state parliament in Melbourne.

The rallies were inspired by Greta Thunberg, who protests every Friday outside Sweden's parliament, demanding leaders do more about climate change.

Sydney student Siniva Esera said Australia needs to be the big brother to the low-lying Pacific islands, including her relatives on the Tokelau atolls.

"Our prime minister thinks we should be in school right now, and maybe we should," the Chifley College Senior Campus student told the Sydney protest. "But how can I just sit by and not do anything to protect the future of this planet, and as my family on the islands worry about the rising sea level?"

Forest Lodge Primary school captain Lucie Atkin Bolton said she'd learned in class that leaders need to look after everybody and take responsibility when things go wrong.

"I wish I lived in a country where our adults, especially our politicians, actually cared about my future," the 11-year-old said.

Canavan, the resources minister, said he's on the side of science and wants Australia to develop all energy sources, including solar and coal. He said he'd rather the kids learn about mining and science.

"These are the type of things that excite young children and we should be great at as a nation," he told Sydney radio station 2GB. "The best thing you'll learn about going to a protest is how to join the dole queue."