Happy Homework 2.0: effects on 24-hour movement behaviours in children—findings from a pilot cluster randomised controlled trial

Abstract Background Children’s 24-h movement behaviours—physical activity, sedentary behaviour, and sleep—are critical to health and wellbeing, yet many fail to meet recommended daily guidelines. School-based health interventions offer a scalable approach to improve movement behaviours, though their impact may be limited by competing academic demands. Homework presents an opportunity to extend the reach of school-based health interventions into the home environment. Happy Homework (HH 2.0) was developed as a digital intervention to integrate movement-based activities into home routines. This pilot study evaluated the feasibility, acceptability, and usability of HH 2.0 among primary school children. Methods An 8-week pilot cluster randomised controlled trial was conducted across four primary schools in the West of Scotland, with classes randomly allocated to intervention or control. Feasibility, usability, and acceptability were assessed using basic app-usage analytics and questionnaires completed by children, parents and teachers. Secondary outcomes included physical activity, sedentary behaviour and sleep measured via activPAL devices, which provided multiple posture- and movement-based metrics. Self-report sleep questionnaires were included, with children’s motivation measured through basic psychological need satisfaction questionnaires. Linear mixed-effects models examined group by time interactions, accounting for clustering by school and repeated measures. Results A total of 82 children aged 8–12 years were recruited (60% of those invited), with 87% retained at follow up, indicating good feasibility. App-use analytics indicated repeated engagement, although overall use was modest, defined by declining frequency and duration of interactions over time. Secondary outcome data from activPAL devices demonstrated a significant group x time difference in sedentary behaviour, with greater increases in the intervention group compared to the control (B = 66.2 min/day, p < .05). Self-reported sleep also showed a significant group × time interaction, with smaller increases in reported sleep duration in the intervention group relative to control ( p < .01). No other significant group × time interactions were found for other secondary outcomes. Conclusion HH 2.0 was feasible and acceptable as a homework-based health intervention however, engagement levels likely limited its effectiveness. Findings outline the potential and challenges of digital school-based health interventions and emphasises the need to strengthen implementation strategies, sustain engagement, and enhance parent and teacher involvement. Trial registration NCT07631754 (retrospectively registered).