I would look at quality of schools for ability to learn/happiness/ well-rounded education not just for pure academic outcomes.
So do you live in an area with nice state secondaries where most children listen to the teacher and want to learn. Or like me, one where there will be a proportion who can't/won't learn (often due to previous trauma poor things), will swear at the teacher and throw the whole lesson off course. And mock those who do want to learn. Because I have taught at that type and it would be a cold day in hell before I sent my own child there.
Even smaller issues like proportion of the class with severe SEN or EAL. Wouldn't have said this was such a problem ten years ago but with funding cuts, some of the children who I provided a lot of support to, with a dedicated TA, no longer get that support they need which can affect the whole class, particularly with larger class sizes.
Pastoral care - in an independent with good counselling provision and a medium level of need, your child will get seen. In a state school struggling to pay for enough days with a counsellor and severely traumatised children needing support, your child won't get a slot or the HOY won't get round to seeing them.
Note- this is clearly not all state schools! I have worked in inner city in deprived areas. But deprived areas that are fashionable with certain middle class Londoners.
I went to a more regular state school myself and it was fine although not in the slightest a well-rounded education.
So my priorities are:
- settled environment
- good music/drama/art/sport provision
- excellent pastoral care
- academic stretch
- somewhere where my child is known, not a face in a crowd.
- good school leadership as some of the issues I've mentioned above can be tackled if you have the right leadership with the right priorities in place
If I can find a state school like that when my children are secondary age then great! But the current funding difficulties in state secondaries are making these schools more elusive.