An enormous problem in state schools at the moment is the levels of SEN and the lack of funding, support and training. Can't speak for private as I rarely get involved with them.
That's aside from the other enormous issues of a general lack of funding/overstretched budgets, teachers having to work ridiculous hours with ridiculous expectations upon them and being made ill from the stress of it all, etc etc.
I'll caveat this by saying that I work in SEND (not in/linked to a school) and also have a child with SEND and an EHCP in a state primary. So when I talk about the children, know that I am not for one minute blaming them, their parents or the schools. You will of course have a handful of awful parents/teachers etc, but these are not the majority. Most parents are desperate to help their children and hate being seen to be 'that parent' in order to make that happen and most teachers are stretched beyond any acceptable level trying to achieve the same aim.
A key issue is local authorities having their fixed view that 'inclusion in mainstream' is the aim. At all costs. It's fucking nonsense, pardon my french. Inclusion in mainstream for children with SEN is wonderful and should absolutely be encouraged IF it's right for that child and IF they can obtain a place at a school that can truly meet their needs. Inclusion at mainstream for lots of children is not appropriate, not do-able, and actually leads to the children not coping and eventually either being formally excluded or removed from school by their parents because they just can't cope with it anymore. Someone posted a link to a report that was recently published over on the SEN education board a couple of weeks ago and a corresponding protest by parents of children with SEN in one county. The report is absolutely hair-raising and heartbreaking. I encourage you all, especially teachers/school staff, to have a read.
My child does receive the support on her EHCP but only because I have the background, expertise and time to be able to (re)write an absolutely watertight (specific, quantified and detailed) section F, lock horns with the local authority when they piddle about arguing trying to make things woollier and trying to remove things that they shouldn't, and ensure that it's followed at school. Most parents do not have the background that I do so I understand why lots of EHCPs are just aren't worth the paper they're written on. My child's very first one was crap.
I see, in schools that I visit for my job and at my own child's school, (mainly primaries, I work less with secondaries) that you have classes now, where you might have 30 children and it's not uncommon for them to have at least 6-7 on SEN support, at least 1 with EHCPs probably 2 so that's around a third of the class. You've then likely got others who are flying under the radar because they're not disruptive but still need more help, perhaps they have a specific but as yet unidentified learning difficulty or they might just be finding it hard to grasp certain skills. The teacher has to maintain behaviour, support the children with SEN differently (and each of them will have differing needs), abide by the EHCPs and then alongside all that, actually teach, mark, review etc! It's an impossible ask. Especially given that most teachers have very little specific SEN training. When you're looking at younger (reception/KS1) children too there is a much higher prevalence these days if things like not being properly toilet trained even with no SEN. Lots of Y1 classes have children who haven't mastered this yet and that causes yet another headache for the staff.
I know of one class at a primary just over the county border from me that's a prime example. KS1, 30ish children mixed year group. They have 10 children on SEN support for varying reasons, 2 with EHCPs, 2 with EHCP assessments in progress. There's are a further 2 who likely will be on at least SEN support very soon. That's half the class! There is a class teacher, two 1-1 TAs for the EHCP children and 1 class TA who is supposedly for the class but ends up split between the 2 children who are going through the EHCNA process. Both of these children need 1-1 support at least some if not all of the time, without a doubt. Without it, they are highly disruptive, very violent to other children and adults, destructive to property etc and at least one of them leads to classroom evacuations probably once a week. You cannot take eyes off them. It's not their fault, their needs are not being met fully and they're lashing out. Totally common, almost expected for children with some types of SEN. But realistically how much can a school take? It is ridiculous for a mainstream classroom of approx 30 to have - if they get what they need along with the other EHCP children - a teacher and FOUR 1-1 TAs assigned to specific children.
Some children with SEN, when properly supported, can thrive in an inclusive mainstream and truly love going. My child is one of them (at the moment!). I am extremely lucky. But for those children whose SEN means that actually they are unlikely to ever be able to access the curriculum or behave in such a way that doesn't hurt people, or manage their day without significant and harmful levels of distress themselves, inclusion in mainstream is NOT the answer. Sometimes, nor is the current 'bar' for special schools. There is a whole group of children with SEN out there that would never qualify for a special school place or actually do well there especially if they have no learning difficulties (I see lots of neurodivergent children, generally autistic or with ADHD who're averagely to extremely academically able) but equally who will never cope with a traditional mainstream classroom environment.
The answer for these children is enhanced provision/hubs within mainstream schools. There are a few cropping up now and for the most part if they're staffed with experienced and well trained in SEN teachers they're great. But they're not common, spaces are rare and they're not well funded. Let's be honest which school can afford these days to fund this sort of thing themselves. Where do the staff come from?
If the local authorities and the government fixed the issues with SEN in schools and dropped the 'inclusion in mainstream at all costs' bullshit then that would go a LONG way to resolving some of the issues that schools are experiencing. Wouldn't fix it all, of course.
You'll notice in my (very longer than planned!) post I've barely mentioned the children in class without SEN. That's telling isn't it. The class teachers that I frequently see barely have time available to pay to them either, and that's not right. All children are being let down by this shitshow, as are the parents (who are often blamed) and teachers (ditto).
I wouldn't be a teacher if you paid me ten million pounds a year.