This guide aims to help develop a shared understanding of the teaching of computational thinking in schools. It presents a conceptual framework of computational thinking, describes pedagogic approaches for teaching and offers guides for assessment. It is complementary to the two CAS guides published in November 2013 (Primary) and June 2014 (Secondary) in supporting the implementation of the new National Curriculum and embraces the CAS Barefoot and CAS QuickStart Computing descriptions of computational thinking. Computational thinking lies at the heart of the computing curriculum but it also supports learning and thinking in other areas of the curriculum.