This only applies to the grammars in and around the major cities I think, not your normal bog standard grammar in the counties. Good on these parents and children - they’re focused, hard working and the kids are respectful so there aren’t as many behavioural issues. Many white British parents are not prepared to put the work in or see the preparation as tantamount to child abuse. Fair enough too.
Once in, especially at the super selectives, the work goes at a cracking pace so kids do need to be hard working and motivated to keep up. They don’t suit everyone.
By the way a lot of these schools also have great extra curricular opportunities and great music and sporting opportunities. These children can do it all contrary to popular myth that it’s all hot housing and nothing else. They have the school support and parental support to access it all.