This thesis is presented in two volumes: the research (Volume One) and clinical (Volume Two) components. Volume One presents three research papers focusing on understanding and addressing stress and wellbeing in school teachers. The first paper is a meta-analysis of mindfulness interventions for teacher wellbeing. The second is an empirical study examining the role of the teacher-student relationship in teachers’ emotional responses to student behaviour. The third is a report written to disseminate the research findings to teachers and teacher training organisations. Volume two consists of five clinical practice reports (CPRs). CPR One presents two formulations (using cognitive-behavioural and psychodynamic models) of a forty-eight-year-old man presenting with symptoms of low mood. CPR Two is an evaluation of therapy drop-out in a primary care talking therapy service. CPR Three describes a single case experiment evaluating a positive-behaviour-support intervention for a seventy-eight-year-old man diagnosed with dementia. CPR Four presents the assessment, integrative formulation and intervention conducted with an eighteen-year-old woman with a diagnosis of a mild learning disability, who was behaving in ways that her mother found challenging. The abstract of CPR 5 – an oral case presentation of an eleven-year-old boy with a diagnosis of obsessive compulsive disorder – is also included.