Data analysis
Multilevel Modelling (MLM), conducted via SPSS Version 26, was used to analyse the data with a mixed design to evaluate the effectiveness of the Guide intervention by examining change over time (from pre-intervention to post-intervention) in the two groups (intervention vs control). School was entered as a random clustering effect for all analyses. Effects sizes for change in scores on the KAMHS subscales due to the intervention (and for the control group) were calculated (Hedges G). Missing responses were pro-rated to the scale mean. If more than 50% of the items were missing from the questionnaires, they were excluded from the analysis. A minimum of 10% veracity checks were completed on all data entries. Due to the nature of the research, the researcher was not blinded during the analysis.