A nine-year-old schoolgirl sparked intense debate in Australia on Wednesday after refusing to stand for the national anthem to protest alleged institutional racism.

Student Harper Nielsen was given detention last week for not joining classmates in a rendition of Advance Australia Fair, a song she says ignores the nation's indigenous people.

"When it was originally written, Advance Australia Fair meant advance the white people of Australia," she told national broadcaster ABC after the incident was reported by local media on Wednesday.

"When it says 'we are young' it completely disregards the Indigenous Australians who were here before us."

Aboriginal culture stretches back tens of thousands of years before the British began colonising Australia in the late 1700s.

They remain among the most disadvantaged Australians, with higher rates of poverty, ill-health and imprisonment than any other community.

Harper said she arrived at the decision to protest herself, but had discussed the issue with her parents.