"Distinguished Achievers in the HSC are no longer found in lower (socio-economic status) schools in anywhere near the numbers they were a decade ago," said the paper's author, principal-turned academic Chris Bonnor. "Those well placed to do so are walking away from less advantaged schools at an increasing rate. "If we track school-by-school results over a long period of time a story emerges about diverging schools, with widening gaps between those seen to be winners and those judged as losers." Mr Bonnor said so-called school shopping tended to be more about seeking out peers than school quality. Advantage or disadvantage refers to a student's socio-educational background, which takes into account their parents' job, education and credentials.

Research author Chris Bonnor says distinguished achievers in the HSC are no longer found in lower (socio-economic status) schools in anywhere near the numbers they were a decade ago. "The research shows that when it comes to school choice, people want to move up the SES ladder," said Mr Bonnor. "They want to send their kids to a school where the kids are either like their own, or more advantaged." Some schools chose advantaged students by charging fees or setting tests, but popular public schools could also influence their cohort by selecting advantaged out-of-area applicants. "The effect of this separation of student by their SES is to cement benefits at the high end of the school SES scale while increasing the disadvantage for students at the lower end," Mr Bonnor said. His analysis found that in NSW, the proportion of HSC distinguished achievers (students who achieved a result in the highest band) from the most advantaged schools grew by five per cent to 18.49 per cent - at total of 65081 students - between 2009 and 2017.

Over the same period, the number of distinguished achievers at disadvantaged schools (with an Index of Community Socio-Educational Advantage of below 1000) fell by 246 to 3575. The most advantaged schools (with an ICSEA of above 1150) in NSW also increased their proportion of students from the top quartile of advantage by 13 per cent. At the other end (schools with an ICSEA of below 1000), the proportion of students in the lowest quartile increased by nine per cent. "[This suggests] students who are potentially distinguished achievers are moving to the higher ICSEA schools, taking their higher scores with them," Mr Bonnor's report said. The paper also finds that the number of distinguished achievers has grown in urban areas, but stagnated in the regions. Mr Bonnor said governments should focus on supporting low SES schools. "There's so many conversations about that since the Gonski report, but that data about how we resource schools shows we are not doing it," he said.