WIBU if I complain about this teacher?

Absolutely. He's a complete thug.

Yet again, in your OP you said he turned back to ‘say something’ so which version is he nailing to the mast before he’s having this conversation with the police?

Each time you’ve commented you have come back with versions of the same comment - the teacher was wrong and you are bothered about your sons actions despite pretty much everybody saying you are unreasonable, you don’t think you are. You and your son are the issue here.
You and your son are the reason why people working in schools are signed off sick.
You and your son are the reason why people leave teaching.
You and your son are the waking embodiment of the diminishing respect for professionals in the public sector.
You and your son are the problem.
I get you are worried about him and so you should be but you are definitely unreasonable to go for this teacher.

I think you have got the right name OP

He said that she did it as he was walking away.

No, he didn't. He said she did it after he turned back. In those circumstances it was entirely reasonable for her to be concerned that he turned back in order to attack again.

What on earth did your son think he was doing? Isn't he ashamed that he presented such a threat that she felt she had to push him away?

A lot of school staff are trained in methods to safely handle children exactly for situations like this. Even with older primary aged children it can be scary to have to use them let alone when your faced for four 14 year old boys.

I hope the school is taking things a lot more seriously than you are.

Can you not see the child was being kept with the HOY because they were hiding him from your son? So they knew something was brewing. And they were right.

Other children are at school trying to learn. That's actually what the teacher is trying to do you know.

In my experience of working with teenagers, the sort of kid who is willing to assault another child in front of their head of year - in a pre meditated attack; not with the excuse they got carried away in the heat of the moment - is unlikely to respond to a calm and hands off request to stop what they are doing. 100% team teacher. You have hopefully seen from the response that YABTU. All the best of luck with your son.

You also need to be doing more than “looking into getting him help” looking into suggests having a glance in the yellow pages for a handy man for a non urgent job. Not actively and physically parenting and getting the support that your son urgently needs

What a lack of respect you and your son have shown for authority.
Do you understand at all how easily you could be on here tonight saying my son punched another kid and now that kid is in the hospital,or worse, and you would be saying there was a teacher there why didn't she stop him!
Did you even consider that maybe the other boy was in isolation to protect him from your son?
Has he come home ready with his excuses as to why he did it, did he downplay what he did and make a big deal out of what a teacher had to do to defend herself and another student?
Seriously you would be so unreasonable to complain.
Take some responsibility here op.

You need to focus your energy on your child right now and what lead him to think he could behave like this? Why did he think it was ok to use such violence against a peer, who was confined and helpless, as well as bring others into the mix to cause more harm?
The teacher was most probably fuelled with adrenaline, especially if she is quite a petite woman, surrounded by strong teenage boys who just unleashed a violent attack? Why don’t you put yourself in her shoes? She was safeguarding the child that was injured.

This times a million!
He went back at the boy through the teacher by your own description so more than necessary she did what she did.

The violence your son perpetrated on this other boy was unacceptable as he caused this situation to escalate.

No wonder we are screwed as a society if this is the take away.

This is almost certainly true. Imagine the mindset of focusing on a teacher possibly pushing him (she probably barely touched him, in reality, but it’s irrelevant) when he’s gone in and punched a child. This is a young man who has never properly been held to account for his own behaviour.

Your son led a mob to find and assault a younger boy, he is a coward and a scumbag. You have more to worry about than a teacher lightly pushing him to stop him. Your thoughts about reporting this lady tells us all we need to know about your parenting and how he has ended up that way.

Your son should be permanently excluded for an unprovoked violent attack. I hope he is. He sounds vile. You need to seriously stop looking for someone else to blame here. It is your son and your son only who are at fault here.

So, you say he "got out", then turned around and she pushed him. Did he come back in? Or had he not left, was still close to the teacher and engaging again with the younger boy he had been assaulting? Do you think she should have waited to see if he punched him again?

Wtf do you expect her to do when your child is attacking another child? Yabvvvu

You said he was turning back to ‘say something’ in your OP so which is it?
Having been in a similar situation I reckon he was more than likely so aimed up that he was turning back for another go at the younger boy!

if this happened back in the day your son would have been quite rightly and literally slapped into shape, shame those rules don’t apply today. you’re the reason little boys like your own behave this way. no respect for anybody, you should be ashamed of yourself

I'm totally sure the word of your thug of a son can be trusted 🙄.

That poor teacher, no wonder they're leaving in droves. Being surrounded by a group of 14 year olds, no doubt much bigger and stronger than her and already acting violently and yet the parent (and I use that term loosely) wants to complain about her behaviour.
Let's hope he's excluded sharpish so she can feel safe in her place of work.

Holy shit, honestly don’t understand what the hell I am reading. This is what’s wrong in the world today, zero respect from parents so why would the kids have any?! No wonder every single day it feels like we get news of another beating/stabbing/murder. Take a long hard look at yourself to figure out why your son is behaving the way he is.

You’ve got much bigger issues with your son than this teacher.

If I were you, I’d be grateful the teacher stopped your son and his accomplices from getting to the other lad. I imagine he’d have been in an extremely bad way if she didn’t given the number of kids who were going to assault him. I think I read that right. They could have battered him.

I’m a teacher. It’s really upsetting breaking up a fight when on duty, even when it’s just between two kids and other staff are helping break them up.

This thread is yet another piece of evidence to explain why our children are far too often being taught by supply teachers who don’t specialise in the subject.

Shameful behaviour - from your son and you.

The only unreasonable behaviour in this case is by your son. He went in to a room with three of his mates to attack another child in front of a teacher. This in itself says he thinks he can do whatever the he'll he likes in school. The teacher was entirely within her rights to push him away (assuming he's actually telling the truth). He should be excluded, he's a danger to the other students and to the staff.

So at 14 your son is in Year 9. I work in a school and am not very tall, virtually all the year 9 boys are taller then me and even some of the year 8's.

Imagine being confronted with 4 boys who are all taller then you and are attacking a younger student.

I'd be shit scared, she was very brave to step in and try to protect the younger child. She's probably still in shock as no one expects that sort of violence when they go to work.
She used reasonable force, and I'm afraid your probability isn't telling the truth as to what happened.

Apologies to the teacher and sort your son out, and be really grateful if the police don't become involved as he could end up with a criminal record.

Day in day out we deal with this in school. You have no idea what a battleground it can be..thanks for your support OP.