Breakfast club has no other set activities?! Not even a few balls or colouring things? That seems a bit odd.... a recipe for disaster if I'm honest, who would want to be in a room with several bored 5 year olds?! I wonder whether you could maybe send him in with something to play with? Maybe a fidget toy or a ball or game or something like a colouring book to occupy him. If not, could they give him specific jobs to "help" get the other children their breakfast so it isn't so much like a punishment?
For lunch, would he be allowed to take a friend with him? Is he getting the injuries in the dining hall or in the playground, because if it is in the playground that won't help. Does he like being in the dining hall? If so, have they explored ways to reduce the sensory overload in the dining hall, so trialling ear defenders, specialised dietsry requirements (some kids onlybever have baked potatoes or the same thing every day, some kids have school lunch but supplement it with safe food crunchy snacks from home, for example), sitting on a table with fewer children, set place every time, close proximity to a dinner lady/member of staff, Wobble cushion if he struggles to stay still, visual now and next cards, using chewellery, laminated symbols woth the rules on the table in front of him - 3 golden rules of kind hands, walking feet, food in mouth or something like that etc. If he likes being with his friends at lunch (mine would be devastated to be left out) then it seems like there could be some intermediary steps, then a review period, then something else before it is removed entirely (unless they have already done this). If he hates the dinner hall, then all power to a seperate eating situation, but I would still be asking them to specify how they intend for his social needs to be met. Social thinning for adopted kids is real, and it's important for schools to take preventative measures where possible to prevent this. I would be asking whether this was what the plan would be long term and whether they think this is sustainable practice all the way through until the older years, and if not how are they planning to transition back into regular lunch times.
If staff are finding him too much to deal with, I assume they have allocated time and funding to support him for his AEN and are looking for further official support through an ehcp etc?
Obviously you don't want L.O to hurt anyone or be hurt, but they are only 5. He needs support to reconnect, social support and supervision. I would be asking lots of decisions before agreeing to what is essentially a type of exclusion. Have they got to the bottom of why he was fighting? Is it a misunderstanding, is it an outburst, what steps do staff take afterwards? How often is it happening? Once a week? Every day? With the same kids? At the same time and in the same place? Is he bigger than the other kids or are the interactions balanced (i.e are they just a phsyical bunch or is he always the one hurting others first?) What has worked in the past and why isn't it working now? What triggers have the school noticed? Who are his friends? Are they "appropriate" i.e evenly academically/energetically/socially matched? If not, what strategies do the school have to direct him towards children who are more evenly matched?
If you have doubts about removing him from lunch, then listen to your gut. I'm always dubious about these things because they re rarely sustainable in the long run, if the member of staff leaves or is absent what provision will be made? I would also be asking loads more questions - will he be sanctioned if he refuses to go in the same way he would be a lesson? What activities will he be doing there? Will he have the opportunity to go to the playground afterwards? Will he be collected from class to avoid any chance of him sneaking off (or will that be too shaming/a point of pride for him to show off that he gets a "special" lunch?)
I know this seems like a lot of questions, but if kids are in mainstream and it is deemed they are capable of it, then surely the accommodations should allow them to access as much of the typical activities of the school day as possible, which includes lunch.
I'm speaking about all this as the mother of 2 children who have literally zero qualms about decking another one with a stick if they are angry, and who has had to have several meetings with nursery about how they need to supervise them closely at times of transitions, or toy sharing, and that just telling them that he didn't use kind hands isn't an intervention (lol). Luckily we have managed to direct ours towards making friends with kids who match them in terms of physicality (working out who they are and going on playdates), so they rough and tumble but are quite evenly matched, so me and the other mums just sort of dust them off and tell them to move away if they aren't happy with the level of roughness, which then translates better into nursery.
Also, on another note, we have had to actively teach our boys "fair play" in rough and tumble- so now we have specific rules about consent, only in the mat, no biting or scratching, only hold for 3 seconds then release, all that jazz. I only say that because it gives them a framework of positive physical play and how to "tease" whilst learning the boundaries. It means a lot of narration- "no, look, your brother is crying because you scratched his face, we don't scratch when we are playing, he is crying, he is hurt. How can we make it better?" Etc. I wonder whether developing something like that could support his development of knowing some realistic boundaries with other kids at school If just not hitting is a steps too far right now.
There are lots of different factors at play here, but don't be afraid to advocate for him. It's not too much for them to make accommodations to support him into the usual ebb and flow of school life, nor is it too much to expect to be kept informed about the progress. Any extreme intervention like isolation should have significant impact, and you should be able to have a measurable outcome. If not, then you can question how useful it will be for your particular child and enquire as to what other options are available or have been considered.