BackgroundWe aimed to: (1) identify school-level factors associated with the sustainment of weekly physical activity (PA) scheduled in elementary schools following withdrawal of effective implementation support; and (2) determine teacher’s perceived usefulness of suggested strategies for sustaining the scheduling of weekly PA.MethodsA secondary exploratory analysis was employed of data from the intervention arm (n = 31 schools) of a randomised controlled trial. Self-report survey data from 134 classroom teachers in New South Wales, Australia, collected following withdrawal of initial implementation support (follow-up T1) and six-months following completion of support (follow-up T2) were used. The outcomes of sustainment of weekly overall PA and energisers (short classroom PA breaks) scheduled were measured via teachers’ completion of a daily activity logbook, with results presented as the difference in mean minutes of PA and energisers scheduled at T1 and T2. An adapted version of the Program Sustainability Assessment Tool (PSAT) was used to measure capacity for program sustainability across seven key domains at follow-up T2. Linear mixed regressions were conducted to evaluate associations between school-level sociodemographic characteristics (e.g., school size, remoteness, and type), teacher-reported school factors (i.e., seven adapted PSAT domains) and the sustainment of PA and energisers scheduled across the school week. Perceived usefulness of 14 proposed sustainability strategies was measured via the teacher survey at follow-up T2 and reported descriptively.ResultsNo school-level factor was statistically associated with the sustainment of overall weekly PA or energisers scheduled. Teacher-reported factors in two PSAT domains – ‘strategic planning’ and ‘program evaluation’ were statistically negatively associated with the sustainment of weekly energisers scheduled (− 6.74, 95% CI: − 13.02; − 0.47, p = 0.036 and − 6.65, 95% CI: − 12.17; − 1.12, p = 0.019 respectively). The proposed support sustainability strategy – ‘provision of PA equipment packs that enable energisers or integrated lessons’ was perceived useful by the most teachers (85%).ConclusionsFurther research is required to explore additional contextual-specific, and end-user appropriate factors associated with schools’ sustainment of weekly PA scheduled. This will help accurately inform the development of strategies to address these determinants and support the sustainment and long-term benefits of school-based health interventions more broadly.