The reason why it's bollocks is summed up right there in the SST's headline: "Rich, poor gap widens in schools." In other words, what the data shows, again, as usual, just like all the other times, is that the social class of a school's intake is by far the most important determinant of that intake's educational achievement. So, agonise over the "best" school for your kid all you like - how "good" that school is mostly comes down to how well off the families of the incoming pupils are, which is not something that's going to rub off on your kid. Added to that is the fact that a statistical average tells nothing about individual outcomes - for instance, you could send your kid to a great school and have them get that school's crappiest teacher, or vice versa. Quality of the teacher is the next biggest factor after social class of the pupil, and you can't tell the quality of the teacher your kid will get at a particular school by looking at the school's stats. Unless you want to job-interview every teacher your kid gets, you might as well send them to the nearest school and be done with it.
So, how does that fine example of the peter principle, Hekia Parata, come into this? Via this comment on the report:
"The decile system has a good intention in that it takes into account the different backgrounds students come from but has increasingly become the explanation for everything.
"It is not. Quality teaching and school leadership make the biggest difference so that is where we think our resources are best directed."
Hey, dumbass - your own fucking data says those don't make the biggest difference. It says the biggest difference is that decile thing you think isn't very important. Grade: Not achieved.
The SST's editor is no smarter than Parata. Their print editorial says 'The bottom line is that the best education comes at a price - either paying for a private school or moving to an expensive area in order to get children in to a high-performing decile 10 school. (emphasis mine)
Consider the stupidity of moving to an expensive area to get your kids into a decile-10 school. We know that school "performance" is very strongly correlated with decile; that means either:
1. A high-performing school will cause people in the surrounding area to become wealthy.
2. Wealthy people's kids do better at school.
If the cause of the correlation is number 1, fuck yes rent a house in that area, you'd be insane not to. But if the cause of the correlation is the distinctly-more-likely number 2, renting a house in the area gets you nowhere. It would be the equivalent of noticing that people in the wealthiest suburb have beautiful cars, clothes and hair, and perfect teeth, and imagining that if you rent a house there the same will apply to you.