Many thanks for various comments.
Wonder if anyone know if there is an organization that I can make complaint to. What I want, just to have a record filed - just in case that there is continuing episode.
That's the advice I would like...
As many asked for the full detailed story, this is the more detailed version. (sorry that I didn't mean to trigger a long thread, I was just looking for help as I have only been here a few months)
As this could be a one-off case for one teacher and one student. Therefore, I would like to keep the school name untold. It is an International School
Part 2 of the story: 'you make your finger shaping like a gun'
Last friday, there was a big episode going about 'you make your finger shaping like a gun'. With in short minutes, the boy was dragged down to see the head master.
The key to the story is (1) it was the teacher who mentioned 'gun' first, (2) the boy made no sound or aiming gesture. My son repeated what he did and I had it video clipped. According to him, he said that he was just fiddling with his finger; and he wasn't even thinking of anything - "I was just playing with my finger".
The consequence of the day was that the boy is completely terrified. To this school - according to their activities, such as make the signboard - going into the head master was given a very fearful perception to every kid - given the kid's world is so small and bounded to school. [sometimes, adults bound themselves to workplace as well - that's our world]
To scale this up to an adult story, it sounds to me like the feeling that you find yourself in the situation: waking up in the middle of the night, having DEA storming into your house, putting a bag of white stuff in your hands and accuse you being a drug dealer and take you into custody.
That's probably how terrified a 6.5 yo kid would feel going through such a dragging down 2 floors to the head master room in the middle of the class time.
Part 1 of the story: Grab the collar
This actually happened the month before. However, it could be my fault that I brought this up in the parent-teacher meeting session. This is because of the fact that, one night a few days before my meeting with the teacher, he mentioned the story again before going to bed that "why teacher hurt me; and when I told her that she hurt me...she didn't even say sorry" [as I taught him that if he accidentally hurt someone, e.g. bump into some one by accident, say 'sorry'].
The story on grabbing the collar started from all the kids lining up, while my son was slow in responding to the instruction. So the teacher came, grabbed the back of the collar and pulled him up to stand from a floor sitting position.
We always teach him to tell other adult(s) in the case that he is physically abused by an adult. So he did, first telling his teacher that "you hurt me" and then he told another teacher (teacher X) that his teacher hurt him. But he was ignored.
As his mind was still having the issue on after a month (and asking me that night), I decided (probably wrongly) to bring the point up with the teacher X directly. Disappointingly, the point was simply brushed off with "the boy must have done something irritating the teacher".
All in all, I hope that this terrible experience will just pass away - as sooner or later in life, we will find similar experience of some sort. So having it now at the age of 6.5 may be a little early, but he gotta learn toughness of life some day anyway.
On the other hand, I would like to be sure as well by having some report filing of the incident(s). Just in case something (similar case to the terrifying gun accusation) were to happen.
I don't dare to bring the subject back to school, as it could backfire at my son. The Part 2 could have caused by my mistake of mentioning the Part 1 of the story to the teacher. [Despite the fact that subject of Part 1 was shot down quickly with some ignorant attitude, the conversation between myself and the teacher on that day was fine. - In fact, I only felt the ignorant attitude afterwards when driving home. A bit slow then.]
Therefore, I would like to seek your kind advice because we will probably have to stick with this school at least a few more months before he completes his year and there is opening at another school.