I understand that sometimes, you DO have to maintain rules and show a little tough love. If she was shoving students around to the point that another student could have been injured, you can't just let it go and do nothing. That's not fair to the student who could have been or was hurt. School is not only where you learn facts, but also where you learn how to behave with other people.
BUT a trip to the principle's office to talk about actions and consequences, or going to the school counselor to talk about why she was rough playing, or calling her parents to discuss her behavior and ways to adjust it, or even just telling her that she has to play by herself for a few days as a "if you can't play nice with others, you can't play with others at all" type punishment would have been much more appropriate. Even a basic detention would have been better. She's 9! A detention to a truly regretful 9-year-old will get the message across! She's not Charles Manson who would do it all again, she's a little kid who is sorry!
Putting a child in a baby harness and, from what I'm understanding, basically strapping the child to her seat so she can't get up is not only horrifyingly humiliating, but it's also extremely dangerous. If a fire, a lock down, or any emergency happens, she's tied to her chair in the middle of a mass panic! Even if the harness wasn't binding the child to her chair and she just had to wear it as a humiliation tactic, what if she has to go to the bathroom and can't get it off in time? She's being humiliated enough without accidentally wetting her pants or worse!
Humiliation is, in my opinion, the WORST form of punishment. Most children would be humiliated enough, being called out on their behavior. They're already sorry. A punishment should be a way of illustrating WHY the behavior is unacceptable, not that the behavior IS unacceptable (since they already know that, since they're being called out). Humiliating this poor girl and having the teacher scream in her face that they don't care about her can be terrifying for a girl so young. Encouraging the class to bully her by shouting at her and calling her a baby is absolutely unacceptable!
It's the shouting that really got me. That's terrifying for ANY student of ANY age. I remember a substitute teacher in high school, my freshman year, yelling at the entire class because they were slightly misbehaving, and I remember just running out of the classroom in tears, I was so scared. There's already and intimidating power dynamic between a teacher and a student, so teachers have to be careful with their anger, especially if they teach younger students. Screaming at them like that... disgusting.
This makes me wish tenure wasn't as iron clad is it is now a days. It needs to be a little easier to fire teachers when some of them act this way.