How can you tell if a school adds value?

[Stopsnowing]

Some schools are super selective and admit only the brightest so get fantastic exam results.
how can you tell if a school’s good results are down to its teaching?

Short answer - you can't.

You can look at the profile of students when they came in, compared to what exam results they got. But only if they took SATS. And this only tells you so much anyway as some schools prepare more for SATS so it might be there are inflated results, some students are tutored to a greater or lesser degree, some children peak early or late, some have other things going on in their lives that affect their performance.

And of course none of use have a cloning device, so even if a student does very well in terms of their entry point, we still can't prove they might have done even better at a different school.

I think the results are mostly interesting in picking out anomalies e.g. if you have a super selective school and their results were only average, it would tend to suggest a problem. Equally a school with a poorer intake getting higher than average results might indicate that they were doing particularly well.

The official way to do it is by their Progress 8 score at GCSE (which measures students' relative progress from Key Stage 2) or their Value Added score at A Level (which measures students' relative progress from Key Stage 4). You can search for the school here: www.gov.uk/school-performance-tables

Exactly. The wrinkle being that Progress 8 scores are not available at GCSE for independent / private schools (that's because private primaries / preps don't do the KS2 tests that are used as the baseline). You could look at the A-level value added (VA) scores as a proxy, but they aren't available this year. In any case I wouldn't spend too much time on this. P8 and VA scores can jump around simply due to cohort effects (just ask any teacher) and on average even for the best schools they don't tend to be significantly different from zero over a decent time period.

Be sure the school supports our kids to grow up to be happy, confident, and balanced. It's the best value-add.

By their retention rates.

You can’t because even the super selective schools have pupils whose parents pay and booked tutors for the GCSEs and A levels and sometimes from Year 7 onwards. Therefore hard to differentiate school teaching vs tutor input. This goes for boarding schools too, we know group of six girls, super bright, tutored in holidays etc together as study groups and got to top universities in UK and US. Though we sure the school would take credit for the grades and leavers destination.
Agree with @yeOldeVictorians comments.

Talking about value added of teaching, perhaps the quantifiable measure is teacher/student ratio, teacher turnover and number supply teachers. The exam results and progression (compared prior and after such as progession 8 is very biased).

For other part of value added it is even harder to quantify, some schools facilities can enhance the learning experiences but again the utilities of these facilities for education is down to the specific child.

Some parents will think certain school name badge have value added in students future life while some others rebuke it strongly.

Visit the school and talk to the staff, students, and parents, but again experience can varied by people and time.

I would probably look for the risk factors instead - the potential area that will contribute negatively to DCs education experience and do the deduction not the addition.

I think the results are mostly interesting in picking out anomalies e.g. if you have a super selective school and their results were only average, it would tend to suggest a problem.

Are there any schools that fit this description?

You can't. I live near Trafford which is a grammar area. There is a whole industry of tutors in that area

I didn't think you could.

Academically, I don’t think it’s possible for super selective, as their cohort will have hit the mark ceiling of SATs (if they’ve taken them) and will do so again at GCSE.

Added value pastorally and in terms of extra-curricular opportunities isn’t measured in league tables, but can be gauged by asking current parents, going to open days and gathering information generally.

For example, if you try rank the London Grammar schools by applicants/PAN ratios - it is a ranking of indicated competiveness of entry (regardless catchment or not), you would expect the GCSE (attainment 8 scores) should roughly in line with the same ranking - it is a very accurate predictor.

If there are some schools consistently rank below its entry competitiveness ranking over the years, it suggests there might be some issues on the schools in terms of teaching as it failed fully reflect the intakes potential relatively. Few schools are like this as they have all similar fundings from state, but there are 1-2 Grammar schools as such shows the sign of warning.

I'd talk to the parents of children who have been there for a year or two. To me it was obvious within weeks that ds' senior school is far more effective than his junior school ever was.

I have a happy, engaged, conversant, almost excited ds, rather than a bored, resentful, sometimes angry one. Different child!

Sometimes you can see it in OFSTED report if they say e.g. that teachers don't know what they should expect from pupils and so on. But I am afraid that would need to be the most recent, from 2020 inspection. In the past once a school was proclaimed Outstanding, it stayed outstanding even if it wasn't that good anymore

@preplexJ Tiffin Boys school resemble your description.