The Ministry of Education (MOE) is quering the amount of inappropriate images being sighted on school computers.

In a new audit undertaken by the MOE, 40% of images downloaded on school computers were sexually explicit or objectionable and may breach film and video censorship laws.

Wellington High School has bought powerful protection software costing $6000, and they have dealt with just one incident of objectionable material this year, but other schools do not have the money for the protection.

A sample of 25 schools were in the MOE's audit and a quarter of the computers surveyed had been used inappropriately, involving some 4500 images.

Thirty six percent of those images were sexually explicit and would normally be restricted by law and two percent of schools had images so objectionable that they've been referred to police.

"We are very concerned about the material that has been found and any material is of concern to us irrespective of the level," says Jim Matheson from the Ministry of Education.

Pornography on school computers has previously been scrutinised.

A Christchurch principal was fined for viewing explicit images on his school computer, and 15 correspondence staff were investigated for downloading images.

"The dilemma for a lot of schools, and we face that dilemma too, is that to put in an adequate filtering system - or monitoring system - costs money," says Wellington High School principal, Dan Dempsey.

The Education Ministry has announced extra funding has been put toward school internet safety.