Echo a lot of what's been said here.
We also live in a grammar school area and there are 3 primaries in our town:
School A is perceived to be the best, with high SATS results, an outstanding Ofsted report and a good percentage of pupils passing the 11+.
School B is pretty average all round
School C is perceived to be the worst with very few children passing the 11+ and low SATS results.
But...
School A streams for classes in Reception in the first month and pins the class lists up for all to see. There is good SN provision in the infant school but most SN pupils' parents are strongly advised that their child's needs would be better served at a different junior school with a SN unit attached. The junior school therefore has very few SN pupils. Friend found the Infant school so pressurised for her low-achieving child that she bailed out and sent him to school C where he is thriving (albeit in a low-achieving type way). Parents at school A thought she was barking.
The school has no social housing in its catchment area and not everyone in catchment gets in, even with a sibling at the school. You have to then reapply for the Juniors.
School B has a very mixed catchment area, from £1.5 million houses all the way down to social housing. There is an average number of pupils with SN. Parent satisfaction with the school is high.
School C has a high level of social housing and an above average no. of pupils with SN. The school is undersubscribed and class sizes can be as low as 13. Parent satisfaction is high, staff are very committed.
Are any of the schools "good"?