Internal guidance delivered to international schools in the global financial hub show students are being told not to discuss politically sensitive assignments publicly and that teachers should be prepared to tell pupils that some of their views may be illegal.

The former British colony has been rocked by new national security laws imposed by Beijing which ban secession, subversion and collusion with a foreign country or external organisation after 15 months of pro-democracy protests took over the city. The maximum penalty for the offences is life imprisonment.

IB teachers were told that if a high school student expresses very strong views about local politics in a discussion that may be in breach of the new national security laws, teachers should "explain calmly to the student that his/her views may be interpreted as illegal".

In another scenario teachers were told that students wishing to write an essay about sensitive topics including Hong Kong politics "should not go in the public domain, should not be published or posted on social media and they should not ask for help from outside tutors".

The IB teachers were told they "must not" advocate for Hong Kong independence, illegal anti-government protest or any activity that seeks to undermine the authority of either the Hong Kong government or Beijing.

But they were also told not to avoid sensitive issues all together because it would be educationally inauthentic and a disservice to students.

"It is important for them and for wider society that they do learn about important issues in their society, and that they learn about them in a balanced, objective and scientific manner," the advice states.

Hong Kong was home to the second largest Australian international community outside of London at the start of the coronavirus pandemic. Children of bankers, lawyers, and other Australian migrants often study the IB or the Higher School Certificate, both of which are taught at the Australian International School in Hong Kong.

The principal of the Australian International School Hong Kong, Mark Hemphill, resigned last week due to the challenges of seeing his family in Australia amid the pandemic.

The school, which charges students up to $40,000 a year, is at the centre of a 100,000-strong Australian expatriate population.

International school teachers said last week they were torn between the ongoing political strife in Hong Kong, curbs on freedom of speech and their employment. Australians in the financial services and judicial sectors in the city have also raised concerns about their long-term future in semi-autonomous region.

The anxiety among international educators follows a wider crackdown on local learning materials. Textbook publishers have deleted references to the names of some political organisations including "Hong Kong Indigenous" and "Demosisto".

An education department circular sent out to all schools in July reminded all teachers and students to strengthen "their sense of national identity" and comply with the national security laws.