Education minister Christine Choi said on Friday that a new set of rules on teachers' conduct is to protect them and the sector's professionalism.

Her bureau on Thursday listed what teachers should, and should not do, saying they should protect national security, social order and the public interest, and they shouldn't choose teaching materials with a view to instil biased views in pupils.

Teachers can be struck off for life for severe misconduct, while those who have committed less serious misconduct can be de-registered for a certain period of time.

Choi said some in the education sector had longed for such a code of conduct.

"[The guidelines] are exactly here to protect our teachers, the professionalism. Because as teachers are alerted what not to do, they won't easily do things that are unprofessional," she told reporters after attending a Legco meeting.

Asked how teachers should teach what happened in Beijing in 1989 or the 2019 protests in Hong Kong, the minister said the bureau won't say what should or shouldn't be taught, but teachers should not select teaching materials based on their own stance.

She said the most important thing is that when teachers pick materials, they consider whether these match the teaching target and whether students can learn something.

When asked whether the rules will worsen the recent turnover of teachers, Choi said people who leave the industry or retire have their own different reasons for doing so.

She said she believes teachers will welcome the chance to point to the guidelines to demonstrate to the public how professional the education sector is.