Bullying in the 3rd grade

I was totally shocked during the 3rd grade camp.

All the students picked on one girl, pretty much all the time.
They called her "virus" which shocked me due to how nasty it is to say to someone and the fact that they were insulting her in English!

The worst part was not being able to effectively manage the situation or one incident in particular...

During one break I went to the toilet and I heard the name calling from down the corridor... The toilets are separated by a wall that stops short of the ceiling so you can hear the ladies toilets from the urinals.  I heard the 'victim' come into the girls toilets and she started crying and in Korean she was saying "I am going go crazy, I can't stand it, what can I do, why why why" and was really crying. I rushed back to the classroom to get the co-teacher, I told her what I had heard in the corridor and that she was crying in the toilet.  My co teacher said that she would go and speak to her. Which, after a couple of minutes, she did and the girl came back and carried on as if nothing had happened.  I think she must be so used to it that she ignores it most of the time and recovers her composure quite quickly.  However the bullies were not spoken to (I tried a couple of times during camp, but it just got laughed off and ignored despite my attempts) it just seemed accepted.  There is nothing wrong with her appearance, she seems mentally very normal, here clothes are the same, she doesn't seem poorer than the others - these are the normal reasons for bullying, aren't they? - I just don't get why she is singled out. The other kids wouldn't take paper from her, sit near her, protested when they were told to be in a group with her.  I am determined that if it happens in regular class next year I am going to stop the lesson, with or without the support of the co-teacher and I am going to tell them that it is wrong, unacceptable and I won't allow it in MY CLASS, EVER! and I am going to get the co-teacher to translate it, I regret I didn't do it during camp.

Another thing that worries me is that Korea has a really high suicide rate especially, among young students.  I think there was 3 incidents last year in elementary and middle schools.

It has really upset me, especially hearing her sobbing in the toilet...

However, I think she enjoyed the camp, I made sure I included her and spoke to her during the lessons and break times, but I wish I could do more!