“We are going to discuss with the Security Bureau and relevant law enforcement agencies about how to handle cases of a similar nature in future,” he said.

The teacher, who had faced complaints, worked at the private Alliance Primary School in Kowloon Tong. Pro-establishment media earlier published a worksheet he had set, which asked Primary Five pupils studying life education to answer questions about freedom of speech and Hong Kong independence after showing them a television documentary featuring Andy Chan Ho-tin, founder of the banned party.

Officials on Tuesday revealed that while the deregistered teacher had not taught the lesson plan himself, three others who did were served warning letters, while the principal and vice-principal were both given reprimands.

Freedom of speech or Hong Kong independence? More details on education row

In a statement, the board of governors at the primary school said it would not comment on the case for privacy reasons, as the teacher had left his job.

“The school has a mission to spread the gospel through education and strives to keep the campus politically neutral,” it said.

Yeung and his colleagues had to face the media hours after the chief executive said the bureau’s transparency over the case was “not ideal”. She took issue with the bureau for its unprecedented move – deregistering a teacher for the first time based on misconduct rather than a criminal conviction – without notifying the public until it was bombarded by media inquiries.

But when addressing the heart of the issue – whether Hong Kong schools should be allowed to hold discussions on independence at all – Yeung drew a red line.

When approached by students initiating any discussion on the topic, he said, teachers should explain the fact, enshrined in the city’s mini-constitution, that Hong Kong was now an inseparable part of China.

“They should explain to them why independence for Hong Kong is not feasible in history or under the system and other factors,” he said.

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Officials said the lesson plan drafted by the teacher prescribed 50 minutes of learning about the Hong Kong National Party and Societies Ordinance, through which the separatist group was banned in 2018 on national security grounds.

“It is a very serious case with a premeditated plan to spread a pro-independence message,” said Permanent Secretary for Education Michelle Li Mei-sheung, calling the scheme “biased and twisted”.

The party’s manifesto was covered extensively, the aim of which could only be to spread a pro-independence message, Deputy Secretary for Education Chan Siu Suk-fan said.

She said the class would then spend 35 minutes to discuss independence for Taiwan, Tibet and Xinjiang – all highly sensitive issues for Beijing when involving the subject of separatism.

“The most shocking of all is that after playing a video about the Hong Kong National Party, students were asked to raise their hand if they agreed with the party’s manifesto,” she said, calling it “unacceptable to society and parents”.

The topic was unsuitable for primary school pupils to begin with, Chan said, and the worksheet given to them only asked them to regurgitate what they heard, which only reinforced the concept and ideology the teacher was purportedly trying to impart.

As critics warned of a chilling effect on freedom of speech in schools, opposition lawmaker Ip Kin-yuen of the education sector criticised the government for deregistering the teacher and judging his colleagues based on a lesson plan that might not reflect the actual teaching.

But the pro-Beijing Hong Kong Federation of Education Workers agreed with the Education Bureau’s decision, saying it could protect students while safeguarding the professional image of teachers.