Hong Kong's education chief said Friday that the government will take a firm stance on the misconduct of teachers including misleading students and using biased teaching materials in relation to the city's months long unrest.   

About 80 teachers, including teaching assistants, were arrested for offenses in the social unrest dragging on for more than six months, Yeung Yun-hung, secretary for education of the Hong Kong Special Administrative Region government, said at a press conference.

The Education Bureau (EDB) received 123 complaints about teachers' misconduct related to hate speech, provocative acts, and inappropriate teaching materials, among others, from mid June to the end of November, Yeung added, of which 30 had been dismissed as unfounded.

"We attach great importance to the professional ethics of teachers and will take seriously every case of conviction, arrest and complaint," Yeung said, adding teachers will be suspended upon arrest and will face disciplinary punishment, including de-registration.

The EDB has investigated 74 complaints and taken actions in 13 cases, sending reprimand letters and a warning. If found involved in misconduct behavior again, some of those teachers may also face de-registration.

"The EDB has also started the suspension procedure on a teacher involved in using inappropriate teaching materials," Yeung said.

Concerns about teachers' role in the prolonged social unrest have been on the rise as an increasing number of teachers and students are involved in illegal activities, from blocking roads and vandalizing property to attacking police. Since early June this year, almost 40 percent of more than 6,000 people under arrest were students.

A 13-year-old student was sentenced to 12 months of probation last week for burning the national flag.

Earlier this month, two juveniles were sentenced to rehabilitation center and were ordered to compensate the metro operator about 280,000 Hong Kong dollars (35,900 U.S. dollars) for vandalizing metro facilities during a violent protest.

"In the face of the extremely serious and dangerous situation, we must act hard to correct mistakes and protect our students," Yeung said.

The EDB on Friday sent a guidance paper to schools about dealing with teachers and students involved in illegal activities, Yeung said, adding that the EDB will track how schools handle related cases.