School children should spend no more than half their day on computers.

That's what a group of parents says - amid concerns some kids are spending up to 90 per cent of their day on screens.

'Sensible Screen use in Schools' wants to see evidence-based guidelines around screen use - with the amount of time spent on digital devices increasing as children get older.

It was founded by Auckland physiotherapist Julie Cullen, who told Mike Hosking the amount of time kids spend in front of screens differs hugely between schools.

"There's a real variation in how screens are used in schools, so some schools have moderate, considered device use but some even primary schools have near ubiquitous device use."