Can an explanation of the origins of social disparities in educational achievement be assisted by a critical examination of Bernstein's sociology? This central question is approached by a consideration of the status of Bernstein's socio-linguistic thesis. The focus is on the nature of the explanations provided. The paper asks: What is the explanatory force of Bernstein's structuralism? What is the relationship between Bernstein's sociological explanations and Vygotskian psychological explanations? What are the effects for pedagogy of cognitive socialization mediated by language-use consistent with Bernstein's theory? The answers to these questions may pose a challenge for sociologists of education engaged with Bernstein's sociology.