After school detentions and the law?

One of the women in the Exclusion area.
These women are not teachers, they are independent staff, they run the Exclusion Room along with a pupil chill out area. It's supposed to be a place of calm, for pupils to access help and advice when needed, as well as individual mentoring.
However DD said the lady who sat with them all day (DD and 2 older boys who she doesn't know) was really quite aggressive. It was her who despite watching like a prison guard all day reduced one of the boys to tears accusing him of cheating which I mentioned upthread.
DD had never encountered her before and says she hopes she never does again.
She did say she bumped into the oldest boy in there with her yesterday at lunch who said hello and asked her was she Ok now, he also asked what she got sent there for. When she told him, he said it was mean, gave her a Mars bar and told her she can find him anytime a boy starts on her.
I told her she should probably decline the kind offer, but it certainly cheered her up that an older one checked she was ok.

Thanks @youarenotkiddingme, I'm desperate to avoid coming across as the dreaded "My kid is innoccent" mum! Straight off the bat I agreed that if it appeared she had hit him, especially unprovoked, then detention all the way and we revoked her screen time at home.
It has left her feeling like she can't speak up or stick up for herself. I did explain telling the teacher would've been the better option, apparently the teacher wasn't in the room and I think there's an element of them not gelling anyway (DD says she shouts a lot, isn't very approachable and has had a few in tears). Not that that excuses her reaction.
I've made a formal complaint and it's being investigated so until then, all we can do is reassure DD that it will be sorted. She's just upset it will mean Behaviour Points and be on her record now.

Sorry there seems to be some mistake here. He has not at any stage been punished. DD was never, and has still never, been given the opportunity to give her side. I was told she would be in an initial meeting on Monday, but this was not sought (hence the "my bad" comment from the woman I had the meeting with), and the punishment received by DD was based on his statement and the statement of another who also hit her. At first before half term I was told they had 5 statements all the same, now it's 2 but they "differ". Yet no one, at any time, has asked DD and when she tried to speak up through tears on Wednesday she was told to shut up.
I want to reiterate that I do, 100%, back the school on discipline. If she messes up, sure, she needs to be shown this isn't OK.
However, I fail to see the point of advertising a Behaviour policy with stages dependent on previous behaviour and stating quite clearly all sides are sought before a decision is made, if they then do not follow through with asking DD (or anyone else who isn't mates with this boy and girl) and going straight to the 3rd highest punishment step when she hasn't had so much as a detention or verbal warning (as there have been no other incidents at all).
I was welcoming of advice from the Governor purely because we have never experienced issues like this before, not to mention detentions. I'm not saying she never had the odd blip at Primary for which she was told off (but this was more not doing homework or being a little silly with friends) but as a first time secondary mum it's all new. I don't think she was out of order as she was explaining that the system was very effective but has been irrevocably damaged to the detriment of students like my daughter by a Head teacher who seems to want to run the school with an iron fist but when things go wrong as they have here, locks herself in school and refuses to discuss without it being done officially.
The last thing I wanted was an official complaint, or investigations. I just want to feel that my daughter is safe and supported and dealt with fairly like every other child, not that they decide to silence her, leave her open to further bullying, and act like she's known as trouble as she's not.
I also don't see how it helps to instill discipline which results in 5 periods of education being missed entirely. She wasn't given any work to do, and as all her homework was on the PC in the schools online system, she couldn't do that either. She sat, from 8.45am to 3.30pm, on a chair, and did nothing. She missed core subjects such as English and Science, as well as history and IT. How is that helpful? Surely they could have collected work for her? But then I feel it further suggests that this was rushed and last minute, hence why I wasn't, as is school protocol, given any notification at all.
I hope that clears that up.

Yes that's my (and DDs) worry that he's probably going to find it hilarious, the little sod.
It is so out of character for her, she has a younger brother who has gotten her used to annoying boys(!) and she knows she really didn't handle it the correct way. I think it was last lesson, at the end of a very full on first half term, in a subject she really struggles in, and she did just lash out without thinking. The first thing she said on getting in the car afterwards was she made a mistake, she had hit someone, she knew she would have to deal with it and she did have a punishment at home which she didn't argue with.
Shes a good kid, it makes me laugh that the same week as this has happened with the whole exclusion thing and after school too, her science teacher sent us an email saying how lovely she is and how she works hard and is a pleasure to teach.
I think it's achieved what it sets out to as she doesn't ever want to be subject to the in school exclusion again, but she also said she doesn't think it was fair as they didn't ask why she did it. She also said now she thinks all the teachers will think she's badly behaved.
We already had the good half term report but not enough Achievement Points to go on a special off site treat, or any postcard home saying she is doing well. She even popped in with me when I picked DS up from Primary and she asked the Deputy Head "was I really naughty here cos the school think I am" which was so sad.
It's knocked her, and I really hope they get that and do everything to change that perception.

That's the thing, it's not really changed, it's just not being followed to what it was set up to do.
She said as a result of my speaking to her, she would be raising a question at their next meeting, not specifically naming my DD but asking for the recent data on in school exclusion use and what this was used for.
I think, obviously I don't know the politics and gossip as we've been there for 5 minutes, it seems there is divisions, but I think as well it takes a while for a Heads style to bed in, especially when she replaced a very popular Head who made popular changes. It's often brought up amongst older parents that they miss the openness of the school, but that's nothing new.
I wasn't, fwiw bothered on the gossip, I just wanted advice for what is best for DD in the longer-term

The teacher has already moved DD so he won't be able to pinch her as easily in the class.
She said when she was taken over to the exclusion room, she tried to tell the head of Year and then the women running the room that she had been pinched but was told to be quiet. She said the women in there were horrible, at one point a boy in there had got his maths homework out and done it- bar their pencil cases and books, their phones and belongings are placed in a locked cupboard all day, and when he was told to show one of the staff, she shouted that he was a cheat, and must have a hidden calculator. DD said it really frightened her, and the boy cried and was then told off for this too. I get the whole deterrent angle, it's no doubt supposed to instill better behaviour, however I think there's a fine line between school punishment and unnecessary levels of nastiness. The whole being walked over in silence to get lunch or go to the loo is ridiculous!
It seems the boy has received no punishment at all. Now DD has said she worries he knows he can do what he likes, she can't stick up for herself, or she will be in huge trouble.
I've raised it with the school though, and said the whole situation has been managed appallingly, outside of their own policy, and totally disproportionately. They have, down to their complaints procedure, two weeks to respond.
The sad thing is, on talking to the governor, the in school exclusion was thought up by the previous head. It was in no way meant to be used as it has been, more it was to do that days work and be spoken to, calmly, about their choices. It was a last chance thing though. She did say the current head has, in the year she's been in the role, undone a lot of good stuff put in place, parents aren't permitted on school grounds without an appointment, you can't speak to anyone accept by email, there is one open evening for parent teacher conferences so you're lucky if you can grab 1 minute with a teacher, and she has this whole procedure now for complaints when previously, you could informally chat to governors and then speak to the head with them. I got the impression she wasn't a fan at all. They do try and keep you as far from staff as possible, the whole child missing but management won't speak to me without an appointment really shocked me.