The teachers' union has accused the Education Department of "gagging" heads of independent public schools through new delivery and performance agreements which say principals must contact its media advisers before speaking to a reporter.
The agreement says independent public school principals will ensure "compliance with departmental media liaison guidelines, including contacting corporate communications and marketing prior to making contact with the media".
The clause was not in a former version of the agreement.
State School Teachers Union president Anne Gisborne said the Government was attempting to restrict comment from all public schools.
"In the context of the current climate of education budget cuts, it's their way of gagging any representation in a formal sense from schools," she said.
Ms Gisborne said schools were expected to be highly accountable but unable to criticise conditions under which they operated.
The department said the revised IPS document simply made explicit what was already an accepted practice.
Director-general Sharyn O'Neill said the media liaison guidelines had always applied to all Education Department staff, including those at independent public schools.
"Any changes were already part of their expectations and responsibilities, including these guidelines," she said.
Education Minister Peter Collier said IPS principals had more freedom to make decisions affecting their schools.
"They don't have to phone head office to say, 'Can we change a light bulb'," he said.
Mr Collier said principals faced the same media limits as any other public servant.They could express views through other means but being able to "criticise whenever they felt like it" would diminish a particular school.