The Hong Kong government's announcement that children from the age of six will be taught the dangers of subversion and foreign interference has been controversial, with many teachers questioning the move.

Last Thursday, the Education Bureau released guidelines which state that primary school pupils should learn about the basic concepts of national security, including subversion, secession, terrorism and collusion with foreign forces.

They would also be taught how to sing and "respectfully listen" to the national anthem, and the role of the police and the People's Liberation Army as "protectors" of Hong Kong.

Students in secondary schools would be taught that existing rights and freedoms were not unlimited and be educated more in depth on the offences related to national security. They would also be told about the challenges that China faces and the opportunities that the mainland presents.

National security would be taught through a variety of subjects, including Chinese history, civic education, geography and biology.

Local educator Chan Hei Tung, 30, said teachers were not surprised about having to teach the concept in schools, but he believed it may be "too demanding for a six-year-old to know about complicated concepts such as interference or subversion". "Teaching students just based on what the government instructs is contradictory to the educational principles of understanding diversified points of views and nurturing critical thinking," he said.

Both Mr Chan and the Hong Kong Educators' Alliance warned about fostering group-think.

Mr Chan said students "may simply write you the answer you want in class or homework, but express their own views on the Internet".

The alliance said a key concern is that the guidelines alienate teachers from students and suppress freedom of speech and assemblies, as they encourage teachers to report to the police when students organise any political activities in schools.

"What if students try to promote pro-government or pro-China political activities at school - should we stop them? And will it result in the violation of the national security law?" the alliance asked.

It added that the national security law may be in conflict, as some legal eagles have pointed out, with parts of the Basic Law - the city's mini-Constitution - raising the question as to how teachers should respond when students ask.

Public schools have to follow the bureau's framework on curricula, but international and private schools are encouraged to follow the guidelines "to help their students (regardless of their ethnicity and nationality) acquire a correct and objective understanding and apprehension of the concept of national security".

Mrs Julie Thomas, who is in her late 30s and in public relations, questioned the need for the new rule.

"If it doesn't enhance learning or help to meet learning milestones per age group - aimed at preparing them and getting kids equipped with knowledge to adapt to primary-school-level learning - what are the value and outcomes the Education Bureau expects to shape in the minds of the young and curious? I surely don't want to teach my kids the dangers of expressing divergent views," she said.

But, another parent - who is in finance and did not want to be identified - with two children in private schools, thought it was "good to learn about what the rules are in the territory". "Every territory has its own rules. If we don't like it, we will move. I don't think parents who put their kids in international schools are bothered much as they have choices, but Hong Kongers will feel angry that the world they know is changing," he said.

Under the guidelines, schools are urged to organise various game activities, such as puppet theatre and board games, to improve children's understanding of the security law.

Those in kindergarten should learn about traditional festivals, music and arts, and develop fondness for Chinese customs to "lay the foundation for national security education".

The guidelines also state that schools are responsible for stopping students and teachers from participating in activities viewed as political, such as singing protest songs or wearing badges to show support for the protests in 2019 and forming human chains or shouting slogans.

Teachers and principals are required to inspect noticeboards, remove books that endanger national security from libraries and call the police if they suspect any breaches.

Beijing imposed the national security law in Hong Kong in June last year after the city's leadership failed to quell the unrest in the preceding year. Mainland and pro-establishment Hong Kong officials blamed the months of protests on students who they said were misled by foreign forces.

The police said that as at Feb 1, 97 people have been arrested under the law, and eight people prosecuted.