Sex offenses committed by teachers against students have emerged as an issue of concern in Hong Kong, as suggested by the latest statistics about convictions, revocation of licenses and lawsuits against teachers.

Seven Hong Kong teachers lost their teaching licenses because of sex offenses over the past three years, the Chinese-language Ming Pao newspaper reported yesterday. Twenty-five teachers were convicted of offenses, the report said.

The newspaper studied information from the Hong Kong Professional Teachers' Union and counted 32 cases of teachers being sued for sex offenses.

The offenses included secretly videotaping or taking photos, indecent assault and molesting from 2006 to 2008. Twenty-five were convicted.

Education Bureau statistics show 13 teachers lost their teaching licenses because of criminal convictions during those three years. Seven were convicted of sex offenses.

The difference in the numbers raised the question as to whether there are loopholes in the education authority's mechanism for revocation of teaching licenses.

In an article posted on the bureau's website, Hong Chan Tsui Wah, a director of the professional development and training division, explained that an internal working group is following up cases in which teachers are involved in criminal offenses.

If a teacher is convicted of a serious criminal offense, the working group will recommend cancellation of his or her teaching license.

Legislator and president of the teachers' union Cheung Man Kwong suggested loopholes might exist because some of the convictions are still in the appeal stage. Some may be teaching in different schools using different names.

Without giving details, Ming Pao cited an example of a teacher convicted of molesting a 12-year-old girl, who changed his name and got a position at another school. The matter went unnoticed until the school received a complaint about the teacher several months later.

The newspaper quoted an unnamed school principal as saying it was difficult for school administrators to examine each job applicant's background.

Aside from teachers, schools also have positions that do not require a teacher's license, the school principal said.

Cheung said the teachers' union will compare its list of known sex offenders among teachers with the bureau's list next week.

Of the tens of thousands of registered teachers in Hong Kong, only a fraction have been found guilty of offenses, Cheung said.