Judith Collins says kindergarten children shouldn't be taking part in Friday's School Strike 4 Climate marches.

Kids across the country - and around the world - are skipping classes to protest inaction on climate change.

In the small Bay of Plenty mining town of Waihi, students from primary schools and Waihi College will be joined by toddlers from Waihi Kindergarten.

Head teacher Kate Mullaney told NZME while taking part is "totally optional", none of the parents have pulled their kids out of the historic demonstration.

She said the kids understand exactly what they're protesting - saving the environment for their own futures.

But National MP Judith Collins doubts it.

"Let's just be sensible about this - I hate the thought kindergarten kids are being used for political purposes," she told The AM Show on Friday.

"If it was my kid being told 'you've got to go and save the planet today' by the teacher, I'd remove my child from that sort of behaviour. Don't use our kids like that. Let three-year-olds be three-year-olds."