The Wider Outcomes Survey for Teachers (WOST) is a teacher informant-report questionnaire developed to aid the assessment of behaviour difficulties, quality of relationships and exposure to bullying among students identified with special educational needs and disabilities (SEND). This study examines the psychometric properties of the WOST in a validation sample representing 6164 students with SEND (mean age 12 years) drawn from 481 primary and secondary schools across England. Results showed favourable internal consistency using Cronbach's alpha and acceptable model fit using confirmatory factor analysis, both of which were invariant to broad categorisations of SEND. Practical utility and construct validity were also established by testing two theoretically derived hypotheses. The measure is therefore tentatively supported as a useful tool for assessing the wider outcomes of students with SEND.