Yes / Physically active lessons present a key paradigm shift in educational practice. However, little is known about the barriers to implementing physically active lessons. To address this, 31 practising primary teachers (23 = female) from 9 primary schools across West Yorkshire, England, were engaged in focus group interviews. Drawing on the socio-ecological model, findings revealed that barriers influencing the implementation of physically active lessons are multifaceted. Teacher’s confidence and competence, concerns over classroom space, preparation time and resources, coupled with the wider school culture that is influenced by governors and parents, reinforce a didactic approach and act as barriers to physically active lessons.

Yes / Assess feasibility, acceptability and costs of delivering a physically active lessons (PAL) training programme to secondary school teachers and explore preliminary effectiveness for reducing pupils' sedentary time. Secondary schools in East England; one school participated in a pre-post feasibility study, two in a pilot cluster-randomised controlled trial. In the pilot trial, blinding to group assignment was not possible. Across studies, 321 randomly selected students (51% male; mean age: 12.9 years), 78 teachers (35% male) and 2 assistant head teachers enrolled; 296 (92%) students, 69 (88%) teachers and 2 assistant head teachers completed the studies. PAL training was delivered to teachers over two after-school sessions. Teachers were made aware of how to integrate movement into lessons; strategies included students collecting data from the environment for class activities and completing activities posted on classroom walls, instead of sitting at desks. Quantitative and qualitative data were collected to assess feasibility and acceptability of PAL training and delivery. Outcomes were assessed at baseline and ~8 weeks post-training; measures included accelerometer-assessed activity, self-reported well-being and observations of time-on-task. Process evaluation was conducted at follow-up. In the feasibility study, teachers reported good acceptability of PAL training and mixed experiences of delivering PAL. In the pilot study, teachers' acceptability of training was lower and teachers identified aspects of the training in need of review, including the outdoor PAL training and learning challenge of PAL strategies. In both studies, students and assistant head teachers reported good acceptability of the intervention. Preliminary effectiveness for reducing students' sedentary time was not demonstrated in either study. No evidence of preliminary effectiveness on the primary outcome and mixed reports of teachers' acceptability of PAL training suggest the need to review the training. The results do not support continuation of research with the current intervention. ISRCTN38409550.