In this convergent mixed-methods study, the aim was to explore how objective and subjective quality ratings of school nurses' motivational interviewing (MI) correlate whilst also considering the perceptions of delivering and participating in the same MI sessions. Quantitative and qualitative data were derived from seven intervention schools participating in the Healthy School Start Plus parenting support intervention. School nurses were trained in MI and conducted an MI session with parents of 6-7-year-old children to discuss children's physical health and development. Quantitative data comprised objective ratings of school nurses' MI competence using the Motivational Interviewing Treatment Integrity 4.2 [MITI-4] protocol, as well as parents' and school nurses' subjective ratings of the MI sessions. Qualitative data comprised semi-structured interviews with parents and school nurses about their perceptions of the MI sessions. First, quantitative data were analysed using Spearman's rank correlation, and qualitative data were analysed using content analysis. Next, quantitative and qualitative findings were merged. Our findings suggest that school nurses' MI performances were rated and perceived as valuable and family-centred by both school nurses and parents who had left the meeting feeling motivated and empowered to promote their children's healthy behaviours. Nonetheless, school nurses were critical to their own MI technical performance, and they found that reflections were easier to deliver and to self-rate. Overall, MITI ratings were the lowest and parents' ratings were the highest. Future studies should focus on relating clients' subjective ratings of MI with clients' behavioural outcomes.
Keywords: MITI-4; client perspectives; motivational interviewing; school nursing; self-rated competence.