New “hate speech” guidelines under which school staff could be more easily sacked for comments in and outside the classroom could silence discussion of the killing in Gaza in New South Wales schools, teachers and legal experts say.

The NSW government has moved to amend codes of conduct to explicitly prohibit hate speech across the state’s more than 3,000 government, independent and Catholic schools, effective immediately from Tuesday.

The premier, Chris Minns, said the new NSW Education Standards Authority (Nesa) guidelines, announced as part of the response to the Bondi beach terror attack, would follow existing hate speech legislation, but decisions on dismissing teachers who contravened them would not depend on the police prosecuting an offence.

“If it’s clear to Nesa that there’s been there’s been a breach … then sanctions will apply,” Minns said.

The change will apply to conduct outside the classroom, including comments on social media.

The president of the NSW Council for Civil Liberties, Timothy Roberts, a former teacher and education officer at Nesa, said the move risked being seen as an attempt to silence discussion on Palestine in schools and distracting Nesa from its work maintaining school standards.

“Schools should be places where students are free to ask difficult questions, and teachers safe to answer them. It is disappointing the premier does not share the same trust the people of NSW have in their local teachers,” he said.

Sign up: AU Breaking News email

In September, a report by the Australian Palestinian Advocacy Network (Apan) said anti-Palestinian racism had become widespread in Australian schools since October 2023, primarily in NSW and Victoria, and was being used to “prevent and silence” the discussion of the war in Gaza through a “climate of fear, censorship, intimidation and punishment”.

One staff member alleged they were “screamed at” by their principal for wearing a Palestinian keffiyeh and called a “terrorist” and “antisemitic” in front of other staff.

Organiser for Teachers and School Staff for Palestine NSW, Chris Breen, said he was “deeply concerned” about how the code could apply, claiming the 200 members of the advocacy group could be “sacked” for expressing support for the pro-Palestine cause.

“This is a political attack on free speech,” he said. “We think it’s extreme legislation that is targeted at the Palestine movement to intimidate and scare teachers.”

On Sunday, the body vowed to continue using the slogan “globalise the intifada” in response to the state government’s intention to ban the phrase.

On Tuesday, Minns told reporters the new guidelines were “not an attack on freedom of speech … or concern about Palestinians and innocent civilians in Gaza”.

He told 2GB the changes responded to cases where the government had “felt it has been unable to take action” after teachers have been accused of hate speech.

“If you participate in hate speech, even if it’s not on the school grounds, then you’re not the kind of person that we want shaping young minds,” he said.

Under the change, Nesa will publicly amend its registration manuals to clarify that school employees must not have “engaged in a deliberate pattern of immoral or unethical behaviour, including hate speech”.

The deputy premier and education minister, Prue Car, said following a complaint, Nesa would investigate and make a decision on whether a particular comment constituted hate speech, before potentially directing the school to terminate that employment of that staff member.

Nesa is defining hate speech as conduct covered by section 93ZAA of the NSW Crimes Act, a controversial new offence which criminalises inciting hatred on the grounds of race. It became law in August last year, despite a warning by the NSW Law Reform Commission it would “introduce imprecision and subjectivity into the criminal law”.

Roberts said defining hate speech according to 93ZAA was “attempting to build a good house on a bad foundation”.

“It is very easy to say that hate speech is bad and we should protect children from it. However, it is hard and often divisive to try and reach agreement on what constitutes hate speech,” he said.

Prof Luke McNamara, an expert on hate speech at the University of NSW law school, told Guardian Australia he thought it would be inappropriate for Nesa to determine if a hate speech offence had occurred in the absence of a prosecution.

“If a teacher is suspected of having committed the serious crime of intentionally inciting racial hatred, the appropriate course of action is to refer the matter to the police,” he said.

“If charges are pursued, it will be for the courts to determine whether the accused teacher is guilty.”

Guardian Australia understands schools were made aware in advance of Tuesday’s announcement, and must now update their code of conduct, a document all schools require to be registered.

A spokesperson for the NSW Teachers Federation said they had sought discussions with the education department about the assessment of codes of conduct.

Andy Mison, president of the Australian Secondary Principals’ Association (Aspa), welcomed policy that supported school leaders “to maintain schools as safe, supportive and inclusive environments for students and staff”.

“Provided that implementation is supported by clear guidance and professional learning, we do not believe these changes should inhibit the kind of open, respectful discussion that is central to a quality education,” he said.

As NSW parliament resumed on Tuesday for the first time since emergency sessions following the Bondi massacre, the focus has remained on the response to the attack and antisemitism.

The opposition moved legislation for all universities, government agencies and local councils to adopt the International Holocaust Remembrance Alliance (IHRA) definition of antisemitism, a recommendation by the special envoy to combat antisemitism, Jillian Segal, in her July report.

Universities Australia’s 39 members have already adopted a definition of antisemitism – either the IHRA definition or one closely aligned to it – after working with Segal.

Minns declined to comment on the proposal on Tuesday.