Headteachers of Primary schools were invited to participate in this three part study. The approach was made through a flyer both directly to head teachers and through links with the Department for Education via the Bradford Opportunity Area. When schools indicated an interest in the project, meetings were arranged with the headteacher (or member of SLT that responded on their behalf) and information sheets, and opt-out written consent forms were sent to parents. All children in participating schools verbally assented on the day of testing. The first four schools to respond favourably were included in this study. All four schools were based in the Bradford District Area. Three of the four schools were located within the 10% most deprived neighbourhoods in the England (Index of Multiple Deprivation (IMD) Decile 1), and the fourth school was located in IMD Decile 6. Sample size estimates were calculated in alignment with guidelines for Rasch measurement [47]. A minimum of 150 participants was required for each round of this study to provide 99% confidence of item calibration within 0.5 logits (the default Rasch linear scale) and ensure sufficient power to ensure measurement stability across samples.

The sample of 331 children (181 male) was recruited from one primary school in Bradford, in which all pupils (Reception–Year 6; children aged 4–11 years old) participated (m age = 8.33 years, SD = 2 years). Prior to testing, teachers were asked whether they thought each child had difficulties with their motor skills. Teachers were given guidance as to what a child with motor difficulties may look like at the training session. Teachers identified 23 pupils as potentially having motor difficulties in the pilot study.

Three hundred and fifteen children (165 male) participated in round two (n = 315, m age = 8.37 years, SD = 1.83 years). Class teachers identified 45 pupils that they thought had motor problems prior to testing.

Two schools in Bradford were recruited for the final round of testing, in which year 1–6 participated (n = 421). However, the data from one of these schools was deemed unreliable, due to a lack of engagement in teacher training, and little time being allocated for testing (which led to researchers having to come back to lead and score some of the activities). As the assessment tool was not delivered by teaching staff (the intended purpose of FUNMOVES) this school was not included in the final Rasch analysis. The final sample size for the third analysis therefore comprised 168 children (70 male, m age = 8.42 years, SD = 1.92 years). Teachers identified five children as having potential motor skill difficulties.