Evaluation of a School-wide Preventive Intervention for Adolescents: The Secondary Social and Emotional Aspects of Learning (SEAL) Programme

Adolescence is a time during which youth are at an increased risk of developing mental health disorders, yet there are relatively
few empirically validated preventive interventions designed for implementation in the secondary/high school phase of education.
The aim of the current study was to evaluate the impact of one such programme, entitled ‘social and emotional aspects of learning
(SEAL)’, over a 2-year period using a quasi-experimental pre-test–post-test control group design. Our sample consisted of
4,443 students (aged 11–12 at the start of the study) attending 41 secondary schools across England—2,442 at 22 SEAL schools
and 2,001 at 19 matched control schools. Our outcome measures were the emotional symptoms and conduct problems subscales of
the self-report version of the Strengths and Difficulties Questionnaire. Hierarchical linear modelling indicated that the
SEAL programme had no discernible impact upon either of these domains of mental health. Further analysis using data from a
subset of youth whose baseline scores placed them ‘at-risk’ demonstrated a reduction in difficulties in those attending SEAL
schools, but this was matched by a similar trend in those attending control schools. Finally, although there was evidence
that student outcomes for conduct problems were mediated by implementation quality, the associated effect size was very small.
Variability in student outcomes for emotional symptoms appeared to be unrelated to implementation quality. The implications
of these findings for school-based preventive interventions are discussed using three explanatory frameworks—theory failure,
implementation failure and research failure.