Thousands of young Australians are preparing to walk out of their classrooms to demand action on climate change.

It's not the first time they've done it — in November, students filled arcades and city squares, protesting against what they see as the destruction of their future.

This time at least 50 rallies are planned across the country, part of a global movement inspired by Swedish teenager Greta Thunberg.

In November thousands of kids walked out of school. On Friday, many will go again. ( ABC News: Andie Noonan )

The strikes have drawn criticism — Prime Minister Scott Morrison has called for "more learning" and "less activism" in schools — but also support, including from some principals.

Ahead of Friday's School Strike for Climate, we spoke to four young Australians about why they'll be taking to the streets.

Aisheeya Huq, 16

Aisheeya Huq says her activism is inspired by her city and her parents' home. ( Supplied )

After her first year 11 maths exam, Aisheeya will be getting the train from Western Sydney to Town Hall Station to take part in Sydney's instalment of the strikes.

"Politicians that have been in power for so long have let us down," she says.

"[They] need to show us that they are willing to make changes for us and our futures."

Aisheeya's activism is partly inspired by the low-lying home country of her parents.

"My parents came from Bangladesh which is a country severely affected by climate change," she says.

"Many people [are losing] their homes and livelihoods."

She's also watched her home city swelter under heatwaves in recent years.

"I live in Western Sydney where the effects of climate change are also felt to quite an alarming degree," she says.

She says the science on climate change is clear, and the time for action is now.

"If you don't expose yourself to the science that's very clearly presented, then you're not going to try to understand what we are standing for," she says.

"There's so much research going on showing what the world will look like, so many cities and countries will go underwater.

"We can't afford not to take action."

Doha Khan, 17

Doha Kahn believes it's her responsibility to use her privilege to speak out. ( Supplied )

Doha Khan, a student from Adelaide, says she's "very lucky" to have the support of both her parents and her school to go on strike.

"I think a big reason why my mum and my dad are so supportive is that they've always pressed that as people who have privilege it is our job to speak out for people who do not," she says.

"Climate change affects the people that contribute the least to it.

"When you have privilege it's important to speak up."

Doha has specific demands for the changes she wants to see from government.

"We want the Labor Party and the Liberal Party to stop Adani, not allow any new fossil projects to be set up, and commit to 100 per cent renewables by 2030," she says.

"If action isn't taken then this movement is only going to grow and continue as more people get frustrated by the inaction."

Tully Bowtell-Young,15

A school English assignment helped inspire Tully Bowtell-Young to push for change. ( Supplied )

Tully Bowtell-Young, from Townsville, says the extreme weather that has lashed the city recently is a stark example of the effects of climate change.

"The flood we just had wasn't just a normal flood, it was a one-in-100-year event. It was a horrendous flood," she says.

Sorry, this audio has expired The climate kids are coming for you

The flood hit after an extended period of drought, and Tully says it's helped to shape conversation in city that is "quite divided on the issue of climate change".

"Both the flooding rains and the droughts have gotten worse through the effects of climate change, and it's easier to talk to people about climate change when they have experienced it," she says.

But Tully has been on the trail of climate activism for some time.

"One of things that got me passionate about the issue of climate change was article I wrote for a school English assignment," she says.

"So I got passionate about this issue through learning."

Billie Tristram, 13

For Billie Tristram, the drive to fight for climate action started at home. ( Supplied )

For Billie Tristram, also from Townsville, the drive to fight for climate action began at home.

"We are all passionate here in the Tristram household," she says.

"We weren't aware of the school strike in November ... [but this time] we thought let's give it a go and add more people to the mix."

She counts climate activist Greta Thunberg as one of her greatest inspirations.

"I think that what she stands for and how she takes it on board is very inspiring in that it's not all talk and we are trying to get action," Billie says.

"I think the first step is to raise awareness, because the truth can be denied but not avoided."