A survey of schools has exposed a yawning gap in home internet access for school students in rich and poor New Zealand families.

The survey found that at one in six of the country's poorest schools, less than a quarter of students had access to internet at home.

The survey by the state-owned Network for Learning, which provides high-speed broadband to 99 per cent of NZ schools, also found that 56 per cent of the low-decile principals felt the lack of internet at home had an impact on teaching and learning.

"Most class work and homework is cloud-based. Lack of access is a barrier," one school said.

Another said: "Students do not get supported by programmes that others get, and are left behind."

They said school links with parents were also affected because many schools now communicated with parents via apps, online platforms or email newsletters.

Principals of 84 per cent of schools in the richest three deciles say at least three-quarters of their students can access the internet at home to do their homework. But in the poorest three deciles, 15 per cent of schools say less than a quarter of students had home internet access.

Executive director of 20/20 Trust, Laurence Millar, told Mike Hosking the lack of access is having an impact on kids' learning.

He said children who don't have internet access at home are disadvantaged because they are less able to enagage with school work at home.