@Breeze67
You are painting a very oversimplified picture, which suggests you might not have direct experience with how grammar or comprehensive state schools actually operate.
Both state schools and grammar schools use ability setting (streaming). While not universal, many children are intensively "hothoused" from a very young age just to pass the grammar school entrance exams. I know many families and children who went through this. Often, once these kids get into a super-selective school, they ease up. It then becomes apparent that a child might not be as naturally brilliant at mathematics as their peers, struggling to grasp concepts as easily. This is precisely why grammar schools have sets—to cater to differing capability levels.
The same logic applies to comprehensive state schools; they also stream students into sets based on their level of immersion and ability. In a good state school, the top-tier set does Maths and Further Maths—exactly the same as a grammar school—and these students regularly win gold medals in the UKMT maths competitions. In these high-achieving state school sets, the pace of education is absolutely no slower than in a grammar school's top set.
Furthermore, student behavior in the top sets of state schools mirrors that of grammar schools. Some kids are slightly naughty, while others are not, depending entirely on their age. The older they get, the more focused they become because they realise what is at stake.
When it comes to teaching, trust me: managing top sets and grammar school classes is much easier. My own son has been in the highest set for Maths and Science from the very beginning. On top of that, he has two hours of tutoring per week to push him even further. His tutor’s own son achieved st GCSE nine Grade 9s at a grammar school. Interestingly, this same tutor spends two days a week working with students who failed their GCSEs and are retaking them, while also successfully teaching the other extreme-kids from top sets and grammar schools like my son.
He maintains that the curriculum is exactly the same, as Further Maths is included in both, and the top sets in state schools take Triple Science for their GCSEs. He says that at our school ( Catholic state) my son's set is doing quadratic functions and parabolas at the end of Year 8, even though other schools don't cover them until Year 9.
In his opinion, teaching smart, motivated kids is nothing compared to the immense challenge of teaching children who struggle to focus or have limited academic abilities. He says that in our school at the end of year 8 my son set is doing quadratic functions, parabolas that are not until y9 in other schools