The Emotional Literacy Support Assistant (ELSA) programme is a school-based intervention developed by Educational Psychologists in which Teaching Assistants (TAs) are trained to deliver bespoke support to develop the social and emotional skills of children and young people (CYP) (Burton, Traill & Norgate, 2009). A systematic critical appraisal of the present ELSA literature was conducted, focusing on what is known about the impact of the intervention on outcomes for CYP. This highlighted the scarcity of available research which focused on ELSA in secondary settings and the limitations around measures available to evaluate the impact of the intervention. To address this, mixed methodology research was conducted to explore the use of three outcome measures, two standardised measures (Strengths and Difficulties Questionnaire and Emotional Literacy Checklist) and an idiographic measure (Goal Based Outcomes [GBO]) with a sample of secondary-aged young people (N=5). GBO was used as this approach has evidenced success in clinical settings, such as Child and Adolescent Mental Health Services (CAMHs), in evaluating bespoke interventions akin to ELSA. The researcher intended to triangulate the standardised data by seeking feedback from teaching staff (N = 3), but challenges with recruitment and data collection prevented this. Semi-structured interviews were conducted with ELSAs (N = 8) and students (N = 4) to explore their views on using the GBO approach in ELSA. Findings indicate that the GBO data captures richer information about the ELSA intervention when compared to standardised measures in terms of the focus of the sessions. However, the tracking of change over time was limited due to the general nature of goals set. The GBO approach was perceived to benefit ELSA practice by supporting ELSAs’ planning and organisation and facilitating a sense of agency for students. ELSAs lacked confidence in using GBO, and students reflected on their uncertainty about the approach, which suggests that ELSAs would benefit from more comprehensive training and ongoing support to build confidence and ensure targets are SMART in nature. The strengths and limitations of this research are highlighted, and implications for the practice of ELSAs and Educational Psychologists, including directions for further research in this area, are discussed.