One in four school principals claims to see harmful behaviour every day between students - and the Children’s Commissioner aims to address that.

The Chief Children’s Commissioner is calling for regular, publicly reported data about bullying in schools as teachers' unions voice concerns over 'blind spots' in the current system.

Secondary Principals Association President Vaughan Couillault says there's definitions of what constitutes bullying from experts - but it's hard to track and measure.

"When it comes to behaviour management and defining what bullying is, there's lots of grey spaces. Every little conflict is born of different stuff."

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