Schools backing students playing competitive sports, might be neglecting others.

An Education Review Office report's found secondary schools with a high focus on competition in sports, have other students being left out.

Secondary Principals' Association president Mike Williams is surprised by that suggestion, saying it certainly isn't the case overall.

"Most schools, most senior schools, most principals are really focused on providing opportunities for their students. That participation aspect's really strong for us.

"I assume ERO has some schools to back up their claims but I'm not actually aware of any that sacrificed participation for competition."

Mr Williams is also the principal of Pakuranga College, where he said they have both competition and participation written into their strategic plan.

The ERO report found 87 per cent of early childhood centres are doing well promoting good health, but only 62 per cent of secondary schools are doing the same.

The review's been commissioned by the government as part of its anti-obesity strategy.

Mr Williams said there's only so much they can do around the nutrition of their students.

"One of the problems in secondary schools is that students are much older. They have much more flexibility going to dairies and shops on the way to school and after school, and it's probably more of a concern than what actually happens in school."