Hard to measure these things with any precision, given that in ILEA days working class kids were expected to leave school with no paper qualifications at all execept maybe City & Guilds, so they could fix the plumbing in the houses of their betters.
Also, hard to separate out the racist level of funding where even to this day the number of white kids at a school tells you more about whether it's
likely to be properly funded than any other factor.
The ILEA may have done a good job, given inadequate funding and the multi-party consensus that working class kids got what they were given, but London's results were markedly below the rest of the country. Today it's not much better, possibly even worse, but neither set up made it all the way to "good".
In principle though, the ILEA was a good idea. The Tory/Blair idea of self managing schools only makes sense when you look at the pig's ear that local authorities make of education. It is a solution born of despair.
Even the most vague analysis of the delivery of any service tells you that local monopolies with no competition or bankruptcy for poor performers is pretty much the worst system the human mind can devise. The fact that people who have the ability to read think it's even faintly rational makes you wonder if LEA's are run by either people with no brains at all, or smart people trying to undermine British society. The system is inherently flawed, and onre of the smartest people I know has found herself trying to make one work. She can't.
Parents are almost never in a position to make good judgements about schools, British parents especially so, given that we have stupidly bad levels of attainment in that generation relative to other countries.
How can someone who thinks Macchiavelli is a kind of pasta wander into a classroom, look at the "classwork" on the walls and form a view of the quality of history teaching. Could anyone ? Recall that teachers are now "guided" into marketing their schools.
Even smart parents find it hard to to get hard facts. Output numbers may fool Daily Mail readers, but even Labour MPs can see through them, even the ones who think Dawn Primarollo isn't the dumbest creature on God's green Earth.. You need to know what the input is to value the process.
My wife and I make part of our livings through the ability to read documents that vary from the badly written to the actively deceptive, and Ofsted reports are so bad you can't tell whether they are lies or incompetence. They are also usually out of date, making the exercise almost futile.
Even if you get past those hurdles, what can you do ?
Asking other parents has all sorts of problems, not least the huge time lag. The nearest school to me has a spectacularly bad headmaster, yet is loved by parents, especially his zero tolerance view on school uniforms. The pathetic academic results seem to be irrrelevant to them.
Took both of us to work out that even Ofsted, an organisation that tries to find the best in any school, seemed to think it had a bullying problem, but that was all right because the bullies were in uniform.