An Auckland school that's banned phones for years is supporting National's promise to crackdown on cellphone use in schools.

If elected, National will axe phones for all year groups - with some exemptions for those needing the devices for health or learning purposes.

Auckland Grammar School has banned student phone usage for decades.

Headmaster Tim O'Connor says it's a method that works.

"As long as you set the standard and you're applying it in consistent basis, we find students comply- and that gives them a five hour window in the school day where they can actually concentrate on learning."

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