Artificial (in)stability in school value-added estimates — poster, lightning talk and abstract, RSSB 2026

Poster, one-minute lightning-talk slide and abstract presented at the 33rd Annual Meeting of the Royal Statistical Society of Belgium (Antwerp, 19–20 November 2026). Cross-cohort correlations of estimated school value-added effects are the latent stability filtered through how much data we have, who is observed, and which school is credited. Three simulation studies isolate each factor at true ρ = .80: (1) information quantity and model choice, (2) selective missingness, (3) pupil mobility and attribution. The recurring finding: the joint model recovers the correlation while individual schools can still be misidentified. Stability and school identification are distinct inferential targets. Tom Van Ransbeeck (KU Leuven), with Koen Aesaert, Wim Van den Noortgate (KU Leuven) and George Leckie (University of Bristol). Contact: [email protected]. Study 1 is under journal review; preprints of Studies 2 and 3 will be added when available. Context and related work This dissertation belongs to the research line on the reliability and stability of learning-gain and value-added models of Koen Aesaert at the Centre for Educational Effectiveness and Evaluation (CO&E), KU Leuven.CO&E: https://ppw.kuleuven.be/onderwijskunde/en/team/team-coeKoen Aesaert: https://www.kuleuven.be/wieiswie/en/person/00119599 Related projects at CO&E:– Schoolresultaten door de lens van leerwinst: naar valide en bruikbare indicatoren (Schools’ learning gain in Flanders: towards valid and usable indicators). OBPWO policy research, Flemish Department of Education and Training, December 2025 – November 2027; promotor Koen Aesaert. https://research.kuleuven.be/portal/en/project/3H250609– De Vlaamse Toetsen: van resultaten naar leerwinst via twee meetpunten (The Flemish national tests: from results to learning gain via two measurement points). OBPWO 25.03, February 2026 – February 2030; co-promotor Koen Aesaert. https://research.kuleuven.be/portal/nl/project/3H260026 Dissertation project: The role of sample characteristics in the stability of school value-added estimates: sample size, student mobility and sample heterogeneity (registered at KU Leuven as “De rol van steekproefkenmerken in de stabiliteit van de schattingen van de toegevoegde waarde van scholen: steekproefgrootte, leerlingenmobiliteit en steekproefheterogeniteit”). KU Leuven, 2023–; promotor Koen Aesaert.