One school is primary for children who are, let’s not dress it up, extremely disturbed. If a child kicks off in class they are removed from the class and have 1-2-1 in a separate room where they can do what they want. It’s not a school that you can compare to the mainstream population. They don’t punish children because it would be likely to end badly. It’s a glorified day-prison. They are not expected to get ‘results’.
Grammar schools don’t have problems with behaviour because they’re predominantly middle-class, and parents usually are super-engaged in their children’s education. They are academic children who want to learn, are very competitive and achieve excellent results. They are also usually far more conservative and strict than Comps. Uniform policies are insane (at mine we had to have school-regulation everything, including a school scarf, a school apron for DT, school bag, school PE bag, a navy blue coat with no logos, etc). FSM numbers are extremely low (there were 2 girls in my year of 124 on FSM). This will also apply to private schools. They may have a detention policy but the reality is that it rarely happens because the children are so well-disciplined.
You need to look at Comprehensives/Secondary schools in areas with high crime, high unemployment, low GCSE results and the majority of children on FSM. The culture in these schools is one of not wanting to learn, and you’re bullied if you do. Short of removing all the disruptive children and allowing the rest to work, what is the answer? They cannot remove them, there isn’t enough staff to split the classes. By law they have to be at school receiving an education.
Without having parents on-side, teachers are on a hiding to nothing. Without sanctions, these feral kids would run amok.
With respect OP, you sound very naive about the complexities of British culture. You sound like you’re a very engaged mum so maybe you don’t understand that many parents are not like you.
In life there are rules. If you break the law, you’re arrested and charged. In the workplace, if you roll up late every day you’d be sacked. Children have to learn that they need to abide by these rules, and face consequences if they don’t. My own DS (now an adult) has Autism/ADHD and struggled at school with some things more than other NT children. But he had to learn to overcome these obstacles despite his disability. It was hard work but eventually he became more organised.
Sorry for waffling. My own belief is that we won’t improve things until parents are engaged early on. Surestart was starting to show results in this area 15 years ago, but unfortunately now we are back to square one since the centres were all closed down. I also think that teachers are bloody saints in very difficult circumstances.