YMM is an 8-week hybrid (in-person and virtual) school-based mindful yoga program (modified from its original 10-week, in-person design due to complications of COVID-19) informed by the teachings of Radiant Child Yoga. It was designed to teach students about self regulation through the integration of movement, breath, and present-moment awareness. It was delivered in the form of three, 30-minute YMM sessions each week by the same instructor-an individual with training and experience as an occupational therapist and yoga teacher through the Yoga Alliance and Radiant Child Yoga.

The Movement Assessment Battery for Children, Second Edition measures children's motor performance in physical tasks (e.g., threading beads, catching a ball, walking heel-to-toe) through direct observation. Quantifiable criteria (e.g., task completion time, number of successful attempts, number of errors) is measured.

This questionnaire asks assessors (classroom instructional staff) to rate how often a student displays certain behaviors (e.g., taking an active role in learning, making a suggestion or request in a polite way) in the past four weeks that correspond to social-emotional, cognitive, and interpersonal skills. Behaviors are rated on a 5-point Likert scale ranging from 0 (Never) to 4 (Very Frequently). A higher score indicates more social-emotional competence.

The Child Behavior Rating Scale asks classroom instructional staff to indicate how often each student exhibits certain behaviors (e.g., returning to an unfinished task after interruption, attempting new challenging tasks) over the past week. This was completed using a 5-point Likert scale ranging from 1 (Never) to 5 (Always), with a higher score indicating positive behavior.

Post-YMM (or adapted PE) session classroom observations of participants' behavior were conducted by two members of the research team who were masked to study conditions and not part of the school's instructional staff. Behaviors in nine categories (i.e., disrupting one's own or others' learning activity, demonstrating aggression toward staff or peers, engaging in a task, being prompted by an adult, affect, and wearing or not wearing a face mask-required due to COVID-19) were tracked and coded quantitatively. During each 30-minute observation block, three students per classroom were observed twice in 5-minute increments, for a total of 10 minutes each. This structure was implemented to capture potential variations in students' behavior over time. Because most classrooms had six students, the remaining three students were observed in the same manner the next time an observer visited the classroom.