She said the girl would have regarded her, as a teacher, as "the most powerful person in the room".
"The attacker was on the knee of the teacher showing off his prestigious position. The girl felt helplessness, unfairness and anger," she said.
"I needed to do something and do it urgently, something very effective that would console her and register the harm on her emotion.
"I was not only a teacher but also the mother of the attacker. A strong signal had to be sent to the girl and to my son as well that no child in the class was superior to others even if he was the son of a teacher. I had to let them know that the teacher's son did not have the privilege to harm others without punishment."
She said: "Just telling [my son] off and letting him know that what he did was wrong was not enough to repair the emotional harm that the girl had suffered.
"However I was not able to use corporal punishment. I did not want to inflict bodily or emotional harm to my son. I had to find out some other measure very quickly.
"An idea came to me that a gesture would work. I remembered the false strike by hand adopted by my grandmother in Korea to console her grandchildren when they were hit by some object.
"If the child was hit by a stone, the grandmother would pretend to strike the stone. If a child was running and hit the furniture, the grandmother would pretend to strike the furniture with a strong word. Then the child felt his pain was reduced because something had been done to punish the wrong."
She decided to do the same thing with her son.
"I made a big move with my hand and touched the back of [my son], with a reproving word," she said.
"The actual force felt by [my son] would be no more than he felt when I patted him while singing a lullaby to get him to sleep. [He] did not feel any pain, whether to his body or to his emotion. He did not cry."
But she felt that she had shown that the girl's emotional pain "was felt by the teacher and [my son] had been punished".
The teacher's team leader, who saw the incident from about nine metres away, told the tribunal on the first day of the hearing that she saw the teacher "smack" her son and her son then started crying.
But the teacher insisted under questioning that her son did not cry.
Michael Regan, counsel for the Teaching Council's complaints investigation committee, asked how her son could have learnt a lesson from the incident if she only patted him in the same way she did when she was singing a lullaby to him.
The teacher said her son would have understood that "it's a different situation".
When tribunal deputy chairman Tim MacKenzie asked her whether the girl saw her "false strike" on her son, she said: "To be honest, I'm not sure. She was more sad that the construction was destroyed."
She said a separate incident, in which a student teacher claimed the teacher smacked her daughter three times, happened after her daughter spilled water from a water purifier. She denied smacking her.
"I approached [my daughter], held her firmly, and told her with a strong voice to stop it," she said.
The student teacher had said that there was no water involved, and Regan noted that in her first interview with her employers about the incident the teacher also did not mention water and said her daughter "was touching the resources and I was scared she was going to put little ones in her mouth, so I spoke to her very firmly and she cried".
Asked why she had changed her story, she said she was "very nervous and afraid" at the meeting with her employers.
"To be honest, I can't clearly remember what I was saying," she said.
Tribunal member Nikki Parsons, a senior manager for Te Rito Maioha Early Childhood NZ, noted that the teacher had used words like "punish" and "discipline" to explain her actions.
"In an early childhood centre, we tend to use more positive language, and 'discipline' is not a word that we would use, so can you talk to me about, in this incident, on reflection, is there another way that you could have handled that situation?" she asked.
The teacher replied: "Of course. I can use just talk to [my son], or move [him] away to a different area, or hand [him] to another teacher. Those are strategies that I can use if they don't like any physical touch."
