This is an exploration of the ways in which science teachers can respond appropriately to the whole range of pupils in their classes in mainstream schools. The author analyzes the nature of individual differences relevant to the science teacher, paying particular attention to learning difficulties and to high ability. He considers different kinds of response and specific tactics which can be deployed to help the range of pupils who find science difficult to learn, and to extend and enrich the science education of those who learn it with ease. He provides a theoretical framework for differentiated science teaching and practical proposals for effective classroom practice.