Traditional powerhouses netball and rugby are under threat as the most popular sports at New Zealand secondary schools, with basketball poised to dunk them both.

Census figures from the New Zealand Secondary School Sports Council show basketball has overtaken football as the third most-played sport.

On current growth trends, it will become the most popular in 2020.

In 2017 a total of 25,649 secondary school students played basketball in a way deemed by the NZSSSC to be "meaningful engagement" in a school setting.

Netball retains top spot despite their numbers falling to 28,455 while rugby has dropped to 26,951.

Basketball NZ chief executive Iain Potter says his organisation has been working hard to provide more opportunities to meet the increasing demand.

"This is a good problem to have and not a revelation - basketball has been growing rapidly for years now. We also know that we can do a lot more," he said.

The census considered students who participated in a sport provided in-school over a period of six weeks or more or played for a club arranged by the school or a government KiwiSport initiative.

It didn't factor in students who took part in one-off school events such as school athletics or swimming sports.