Impact of School Competition for Academic Students on Secondary School Gain. The Cohort Effects of Academic Selection or Depletion in 22 Australian Independent Schools 

Abstract Book of the 8th Global Conference on Education and Teaching

Year: 2026

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Impact of School Competition for Academic Students on Secondary School Gain. The Cohort Effects of Academic Selection or Depletion in 22 Australian Independent Schools 

Andrew Laming

ABSTRACT:

Current school gain metrics (value-add, percentile growth) are methodologically complex, not intuitive for non-educators and rarely applied outside the research setting. Pioneered by the author, percentile shift analysis (PSA) performs simple subtraction analysis to quantify how student core-skills are ultimately translated into secondary graduation metrics. PSA also isolates the cohort impact of late-arriving or departing students on school mean scores and mean gain. Australian results from 22 graduating Queensland independent school cohorts reveal widespread academic selection and depletion of top decile academic students, associated with commute time from higher socio-educational competitor schools. PSA method will be outlined, enabling any educator to perform similar analyses on their domestic data. This includes mean school gain, quantifying academic selection or depletion, relative school preference for strongly literate or numerate students, domain-specific gain, and student domain disparity. Where graduate metrics incorporate subject selection (ATARs, O levels), domain-disparate graduates appear to outperform domain-balanced graduates by a mean 4% in graduate ranking. A novel compositional effect may explain why significant gain was limited to graduates occupying a dominant academic tier within their cohort, while more academically isolated graduates demonstrated no significant mean gain. These findings challenge conventional notions that students are best served attending the most academic school they can access, suggesting previously unrecognised lower-academic schools outperform top-academic schools but only for those with lower core-skills baselines. Top academic students who underperformed at graduation slipped fewer percentiles attending top-academic schools, further supporting the compositional effect hypothesis

Keywords: gain; literacy; numeracy; assessment; academic selection