Jos Castro Silva, lecturer in sciences of education, and Jos Morgado, assistant professor, both work at the Instituto Superior de Psicologica Aplicada in Lisboa, Portugal. In this article, they describe their study of support teachers beliefs about the academic achievement of school students with special educational needs. The support teachers who were the subject of this study work in mainstream schools where the majority of pupils with special educational needs are educated in mainstream classes run by general teachers. The work of the support teachers is supervised and supported by special education team co-ordinators. The study reported here set out to elicit the support teachers beliefs about the factors that contribute to success at school for pupils with special educational needs. Results suggest that the support teachers consider that factors including school climate, curriculum design and teaching approach contribute significantly to achievements among these pupils. On the other hand, analysis reveals that the support teachers attribute difficulties and lack of achievement significantly to out-of-school contextual variables. These findings are related to a detailed review of the literature and the authors discuss the implications for policy, practice and professional development.