Racist or sexist behaviour, particularly from people in institutional positions of power over others, is insidious and pernicious. It may be gradual and subtle but ultimately it is capable of doing cumulative harm out of all proportion to those singled out. It has no place in a multicultural society and so-called world city like Hong Kong. It is therefore reassuring that the English Schools Foundation has reacted swiftly to complaints by students that some teachers were responsible for such behaviour, or tolerated it from some students towards others. The claims came from students and a former teacher at King George V school, one of 22 campuses run by the foundation. ESF chief executive Belinda Greer has described the complaints as “deeply troubling”. They are to be treated “extremely seriously” at the highest level and a plan to strengthen diversity and equality is to be developed. This follows a Post report that a Year 13 student had accused teachers in an open letter of ridiculing the names of Asian students and making girls feel uncomfortable during uniform checks. An online petition demanding school management address the issue and introduce reforms quickly gathered well over 1,000 signatures. It is too soon to reach any conclusions. The behaviour in question may be relatively isolated and confined in a well-respected citywide institution. But to treat it in those terms would be a mistake. As Greer acknowledged, if the ESF prides itself on the values it holds as an organisation, “we must listen when we hear the experiences [of] some of our students”. The letter claimed some teachers had allowed the normalisation of racism on campus by making “casually racist statements” for years, such as “mispronouncing, misspelling, and mocking names of Asian students” and overlooking racist behaviour. Allegations against teachers will be treated extremely seriously: ESF boss The writer left no doubt that the “Black Lives Matter” campaign sparked by the deaths of black people in police custody in the United States has resonated globally. “The current global climate regarding attitudes towards racism has made me realise I cannot stay silent on the racism perpetuated within ESF schools,” they wrote. Whatever the outcome, the accusers and the ESF have done Hong Kong a service in calling out perceived racist and sexist prejudice. They are poison to a multicultural international hub.