I'm in the Primary Presidency in our ward and was a Valient 11 and 12 teacher for 3 yrs prior.
Teaching, No Greater Call -- a resource guide for gospel teaching
Pres. Hinckley observed, little problems will inevitably occur. Whether you are teaching in the home or at church, your lessons may at times be disrupted by the behavior of those you teach. In your efforts to help those who become disruptive, remember that you should not simply try to correct inappropriate behavior or make sure everyone is quiet: you should help learners become better disciples of the Savior.
--- I have a picture of the Savior and ask them would they act this way if Jesus were in the room right now. After a while I just point to the picture and nothing is said.
There was a time I had two brothers and all they did was find ways to bother each other,
no matter where I placed them in the room. I started having my husband come to class and sit between them -- that worked. I just introduced my husband as 'priesthood' here for a visit.
There are many ways to deal with children who are difficult. I'm not saying that your child is difficult and that justifies what the teacher did. It is difficult sometimes with children but to use the discipline that that teacher used, I feel, was inappropriate. When I have children who are acting out I try to find out what may be causing them to act out.
"Those you teach have divine characteristics and divine destinies. Your responses to their actions can help them remember their infinite worth as sons and daughters of God. Through your example, you can help them increase in their desire to help each other learn the gospel and live according to its principles."
It's very important to remember this when teaching these precious little spirits. We should seek to understand those we teach -- not make fast judgments and go from there.
And finally, as a teacher I would GREATLY appreciate a parent coming and sitting with their child if that is what it took! We (the presidency) just had a situation where the child was not wanting to be away from mom (without going into detail) and we didn't just want to let him go to RS with mom so we invited mom to his class so that he could still be learning the gospel on his level. There are many LOVING solutions to problems.
I do pray that you will find an easy, loving solution to your dilemma.