The academic year started with a student in one of my classes being absent for both unit tests and an assessed practical, despite adequate prior notice.
"She is frequently absent," said one student. "She falls sick a lot," informed another.
My inquiry revealed no specific health issues but continued observation shed light on the group dynamics of the class, where this particular student always seemed to be on the outside looking in.
Her behaviour in class vacillated from asking unnecessary, attention-seeking questions or being completely withdrawn. One day she made repeated excuses for not doing work, so I intervened.
"No one talks to me," she said with tears in her eyes. "I hate coming to school."
Schools generally have strict policies against bullying and foster a climate that prevents it, either through student supervision or by ensuring staff continually educate students.
However, passive bullying - such as ostracising a student - can be difficult to pick up on and address, simply because it is human nature for children and adults to associate with others who are similar to them, or who have qualities that in some way support their own behaviour.
Excluding some students, spreading rumours, divulging confidences and manipulating social relationships to make others disliked is often referred to as "emotional bullying" or "relational aggression".
Research shows that girls tend to be more relationally aggressive than boys, and are also more vulnerable to it especially during their pre-teen and teenage years because of the high value they tend to place on friendships at that age.
The impact of this is often underestimated and frequently goes unnoticed by elders.
In some cases, victims of emotional bullying manifest more signs of mental distress than those bullied physically. Feelings of rejection and exclusion affect academic performance and health, impacting on the grades and self-esteem of the victim.
Research shows a positive correlation between bias and bullying. Prejudice could come from size, ethnicity, race, sexual orientation and religion, to name only a few sources.
Philippe Bera, member of the executive board of the Hong Kong Holocaust and Tolerance Centre (HKHTC), notes that prejudice "stems from being a minority".
"Whenever you have someone who is off the beaten track or someone who is not common, you will always have issues with tolerance," he says.
The HKHTC is holding an exhibition at the Central market walkway called An Oasis of Survival and Hope. It features artwork by pupils from Hong Kong schools and aims to teach local children about the second world war, as well as issues surrounding racism and tolerance.
Kimberly Mann, manager of the Holocaust and the United Nations Outreach Programme, established in 2005, inaugurated this exhibition. She explains that examining the role of teachers in encouraging students to respect diversity is one of the programme's tasks that is not directly linked to the Holocaust.
"This programme has a very broad mandate," says Mann. "It is important there are many different dimensions to this history [of the Holocaust] - not just the victimisation.
"There were resistors, and there were rescuers. The rescuers, in particular, are very good examples for students, because their values are the ones that we are working to instil in our children - social responsibility, courage, compassion and tolerance.
"There is a need to mobilise civil society for education and awareness in today's world."
When I organised an intervention with the students of that class, one of the girls said: "You can't force me to like her or talk to her, anyway."
Very true, I acknowledged. So how does one address behaviour like this? There is only one way. Prevention, by teaching tolerance towards all.
Mann advocates creating an awareness of the pyramid of hate, where genocide has its place at the pinnacle that begins with prejudiced attitudes and can sometimes escalate to acts of discrimination and even violence.
Anjali Hazari teaches IB and IGCSE biology at the French International School