Stability of Primary School Value-Added Scores over Time: A Comparison Between Math and Language Achievement as Outcome Variables

Value-added (VA) models are widely used for accountability purposes in education. Tracking a teacher’s or a school’s VA score over time forms oftentimes the basis for high-stakes decision-making and can determine whether teachers can keep their jobs or schools may receive certain funding. Despite their high-stakes application, the stability of VA scores over time has not yet been investigated for primary schools. Moreover, it is unclear whether different outcome measures (e.g., language and mathematics) may differ in their stability over time. In the present study, we aimed to clarify the stability of VA scores over time and investigate the differences across outcome variables. Furthermore, we wanted to showcase the real-life implications of (in)stable VA scores for single schools, with a focus on an informative use of VA scores rather than an evaluative way. The exploration of school VA scores in primary schools is especially relevant for heterogeneous student populations, for instance, in Luxembourg. Thus, we drew on representative longitudinal data from the standardized achievement tests of the Luxembourg School Monitoring Programme and examined the stability of school VA scores over two years in 146 schools (N = 7016 students). The overall stability, as measured by correlation coefficients, was moderate with r = .37 for VA scores in language and r = .34 for VA scores in mathematics from grade one to grade three. Real-life implications for schools will be discussed.