These statistics list performances by varying proportions of students who sit NCEA examinations. The results map directly on to poverty statistics and are influenced by the level of data-distorting exercises schools choose to implement. These include training in examination technique and strategic content teaching.
When we select a school for our child, what kind of information are we really seeking? Is it ranked performances in whatever assessment rubric is currently being used, or is it the school's ability to grow our child's thinking and confidence?
If you believe it is the later, you might be interested in William Ayer who points out that comparative testing (which heavily influences the statistics you have probably just been reading), does not measure anything approaching the breadth of learning we wish for our children. Such testing he notes, "can't measure initiative, creativity, imagination, conceptual thinking, curiosity, effort, irony, judgment, commitment, nuance, good will, ethical reflection, or a host of other valuable dispositions and attributes. What they can measure, and count, he suggests, "are isolated skills, specific facts and function, content knowledge, the least interesting and least significant aspects of learning."
But trusting performance results contains another problem - one perhaps we don't think about enough. In my job I help students to grow through the last phase of their formal education. The true pleasure of working with PhD students is that you get to understand how an individual thinks and learns over a three to four year period.
Interestingly, many of these very bright people did relatively poorly in school tests. Often this was because they were very deep, reflective or disobedient thinkers. Their intelligence functioned when it was given time to do so. These bright people are not pub quiz performers. Giving them 50 questions to answer in three hours in a streamlined hall provides no indication of the sophisticated nature of their learning.
I work with other candidates who are "finely tuned" thinkers. When we use aggressively blunt tools to understand their learning, they shut down. The brutality of artificially stressful environments (that they never encounter in real life), cause them to underperform what they know and can use. The results by extension give a damagingly false indication of the quality learning environments their teachers have carefully constructed around them.
When choosing schools we need to prioritise much more than ranked test results. Choosing a school is infinitely more serious than scanning ranked examination percentages. We need to know the human heart of a school because design for learning is a complex thing.