Software has been wiped from thousands of school computers because of a row over Government funding.
Microsoft Office programs have been ordered to be removed from about 25,000 Apple Macintosh computers in schools.
The Ministry of Education did not renew its deal for the programs, meaning that students using the Apple computers will not have access to common programs such as Excel and Word unless the school buys the software independently.
It is thought to affect around 30 per cent of all schools nationwide.
Schools in which students use PCs are not affected.
Principals said the move was baffling, as it went against the drive to use computers to enhance learning.
Auckland Primary Principals Association past president Julien Le Sueur said schools were being told to improve links with parents and their communities.
But the outside world was dominated by the global giant Microsoft.
"We've had our legs cut out from underneath us," he said.
Mr Le Sueur, principal of Pinehill School in Browns Bay, said he was told to remove software from 80 Apple computers his students use.
He knew of a high school with 200 of the machines.
Computers used by teachers and office staff were not affected, Mr Le Sueur said.
The problem was over licensing deals said to be worth $100 million over 10 years.
Education Minister Steve Maharey said Microsoft insisted the Government pay a licence fee for all Apple Macintoshes in schools to use Microsoft Office.
But the programs were used on only half the machines.
"The ministry could not justify the extra $2.7 million being given to Microsoft for software that would not be used," said Mr Maharey.
He said Apple supplied a program similar to Microsoft Office, and NeoOffice, an open-source program developed by volunteers, was also available.
But Mr Le Sueur said NeoOffice was littered with problems, and its website warned that users could expect lots of bugs.
"That's not the sort of software we should be expecting kids in New Zealand to be using."
Mr Le Sueur said the ministry took over licensing negotiations for the Microsoft software six years ago to do a bulk deal and remove the costs from schools.
He blamed a budget blowout for the Apple move.
"The ministry didn't accurately predict the number of PCs that were out there and consequently the cost of licensing has gone through the roof.
"They were caught in the situation where the budget they were given to license software was not adequate to do the job."
A Microsoft spokesman said schools with Apple computers could buy the software themselves.
The company offered a less-than-retail deal for schools, and a significant number had taken it up.