Anyone with two braincells to rub together would, without a study or any form of Educationalist mumb0-jumbo, probably come up with the same answer.
A strong Head who kicked out sloppy and ill-disciplined teachers and disruptive kids.
What is certain is that, if left unchecked, the Satanic Embrace of the LEA and Teaching Unions would stop Heads and as likely as not hound them into early retirement or worse.
At one school the benchmark - for what it is - of 5GCSEs rose from 18% to 80%. And no, they did not expel 3/4 of the kids*.
The Fabian entropic model has held sway too long - excuses for poor performance because the area is "deprived", which is, frankly, poppycock. These people WANT a dependent underclass. Ignorant, sloppy and lazy. Damn them all.
Kids are, almost always, a blank sheet. They can all become responsible, thinking, caring individuals. If the area they grow up in a rough area, now called "disadvantaged with a multi-faceted nexus of urban ills", and their parents, for whatever reason, do not provide structure, routine, discipline and aspiration, it is all the more important for the school to provide it. I am not saying schools MUST by central fiat, but if you leave things alone enough parents and professional teachers will create those environments. Yes, society, not the State, will create the environment so that the disadvantaged can climb the ladder. The School can be an oasis of safety, stimulation, order, fun and reinforcement in such areas. Right now, far too many just reflect the degenerating, violent, turd- and litter-strewn streets around them.
This is not rocket science. Schools run as a tight ship need not be brutal dungeons that conceal paedophiles and sado-masochists. If you ask me the real S&M fiends are those who both meddle and stand aside in turn while year after year of children are condemned to a bleak, narrow and grey life where highlights are Celeb Trivia and a Bargain Bucket O'Wings (plus sides). To what end? Oh, I forgot, an endless stream of new "customers" for the Social Services and Educationalists to pick over.
LEAs. Close them all down. NOW.
* 5 marks if you show your working out.