ClothesOfSand ... that's similar to the situation here.
dd missed out on the super selective, she'd have been in the bottom third there on admission with a couple more marks (should we have tutored?). She's a bright kid, top of her peer group with academic interests. She's not truly gifted, not top 10% of grammar girls but the type of child who would make great progress in an environment where expectations are really high. She's not one who will do well anywhere - I don't believe there are many (?any) children who are.
She'll be going to the good comp - 68% A-C including maths & English, teaching rated good, nice facilities, decent area. She won't be able to do a full set of academic GCSEs - no Latin, no classics, no separate sciences, no chance to do two MFLs, no further maths ... they pad the curriculum out with business, law, psychology, dance, Btechs. The pace of the lessons is slower, work load is lower, expectations aren't so great. They get some children leaving with a clutch of A/A/Bs but they never get into the selective 6th forms either state or independent. They can't keep up - those school have already covered a chunk of the A level syllabus by the end of the GCSE years. 6th form leavers don't ever go to Oxbridge, ex-polytechnics is the rule - destinations are more travel & tourism than medicine.
I can't say I'm thrilled about it.
This isn't a situation where the grammar is creaming off the brightest kids - the grammar hasn't got a catchment area & only a tiny percentage of local children get in. There is an outstanding comp in area too - 3 MFLs, separate sciences, impressive leavers destinations, etc etc. Children don't leave for the grammar 6th form because they can do just as well there. Why can one school manage it but the other can't?