This chapter reports on a pilot study conducted into the potential effectiveness of an application (app), titled the Student Engagement and Teacher Reflection App (SETRA), which is being developed as a professional learning tool to assist teachers to cater for the diversity of students in contemporary schools through engaging all young adolescents in learning. Drawing from the evidence-based Young Adolescent Engagement in Learning (YAEL) Model, the app serves to support teachers’ growth in professional learning, which is an important characteristic of teaching and teacher professionalism. The YAEL Model, developed in 2016 by members of the research team, provides a professional learning approach for secondary school teachers to engage all students in their learning, including those at risk of disengagement. In order to facilitate teachers’ access to, and implementation of the many dimensions and characteristics of the Model, SETRA has since been developed as a tool to provide teachers with real time, “anywhere, any place” professional learning. A pilot study subsequently determined proof of concept of the baseline version of the app, as well as its potential effectiveness as a teacher professional learning tool. In this chapter, the YAEL model is first overviewed and then the findings from the SETRA pilot are discussed.