A 12-year-old Perth schoolgirl who dressed as an anti-fracking crusader for a book week parade says she is disappointed after being told by her school to roll down the top of her costume to avoid causing offence.

Claire Hickey dressed as Frackman, a character featured in the documentary of the same name, for Subiaco Primary School's annual Book Week Parade.

Her father James Hickey had taken her to see the Australian-made documentary earlier in the year and she was inspired by the protagonist in the story.

"After seeing the documentary I thought about how he [Frackman] was standing up for the environment and I thought maybe I could do a small part of that," she said.

But when she turned up to school last Friday she was told that unless she rolled down the top half of her costume - emblazoned with the words "No Fracking Way" - she would not be able to participate in the parade.

"I got told by the principal's assistant that I had to take off my outfit," she said.

"She told me it was a fun book week that was being taken too seriously by a political issue."

The Frackman documentary that follows former construction worker Dayne Pratzky as he protests the expansion of the coal seam gas industry near the town of Tara in Queensland.

Fracking 'too close to swear word': teachers

An Education Department spokeswoman said Claire's teacher, along with the assistant principal, had asked her to roll down the top part of her jumpsuit.

The spokeswoman said the word "fracking" was considered by teachers to be too close to the obvious swear word and inappropriate for a primary school.

But the 12-year-old said her teacher actually told her it was a great costume, and it was the assistant principal who told her to roll it down.

Environmental crusader Dayne Pratsky featured as Frackman in the documentary of the same name. ( Supplied )

Claire said she believed it was not the word alone that was the problem.

"She [the assistant principal] did mention the word but she also said it wasn't a day to make a political statement," she said.

"I believe there was nothing wrong with my outfit whatsoever.

"I told her I was standing up for the environment and I thought it was a pretty brave idea."

Mr Hickey said he had warned his daughter she might receive some flak at school for openly talking about the issue.

"Her response was: 'Dad, what could be more important than protecting the environment?'," he said.

Claire eventually decided to take the outfit off for the parade, but said it would not deter her from speaking out.

"I still do want to stand up for the environment," she said.

"But I just hope people don't shoot me down so quickly in the future."