Measuring change in school-based practices that promote children's healthy eating and active living: a psychometric study.

BACKGROUND: Public health interventions targeting youth nutrition and physical activity often focus on changing policies, systems, and environments (PSE) in schools. To support rigorous evaluation of PSE efforts, this study examined whether the School Site-Level Assessment Questionnaire (SLAQ), a self-assessment instrument for schools serving grades kindergarten through 12 (K-12), was sufficiently sensitive to measure changes in schools’ nutrition and physical activity practices in response to interventions. METHODS: This longitudinal, observational study included 69 K-12 schools in low-income California communities that completed School SLAQs in two consecutive school years (2022 and 2023) and reported PSE and/or nutrition education interventions in school year 2022. Wilcoxon signed-rank and paired t-tests compared changes in nutrition and physical activity practices measured by the School SLAQ between years among schools with relevant interventions. RESULTS: Statistically significant increases in median nutrition (by 0.06, p < 0.001; effect size [ES] = 0.42) and PA (by 0.07, p < 0.001; ES = 0.64) overall domain scores were observed among schools implementing corresponding interventions. Statistically significant increases were also observed in six of nine practice areas: school meal and beverage quality (by 0.04 [95% CI: 0.002–0.07]), meal environment and promotion (by 0.04 [95% CI: 0.01–0.08]), non-meal food and beverage quality and promotion (by 0.09 [95% CI: 0.05–0.13]), non-physical education physical activity opportunities (by 0.09 [95% CI: 0.02–0.17]), physical activity facilities (by 0.07 [95% CI: 0.03–0.12]), and nutrition education (by 0.10 [95% CI: 0.01–0.18]), among schools implementing corresponding interventions. CONCLUSION: The School SLAQ is, to our knowledge, the only tool demonstrated to measure changes in the K-12 school nutrition and physical activity environment. This comprehensive and valid instrument can be a valuable tool for schools and public health partners when planning and evaluating the effectiveness of school-based PSE interventions, as well as measuring the impact of policy initiatives.