Comprehensive schools are primarily about providing an entitlement curriculum to all children, without selection whether due to financial considerations or attainment. A consequence of that is a wider ranging curriculum, including practical subjects such as design and technology and vocational learning, which were less common or non-existent in grammar schools. Providing post-16 education cost-effectively becomes more challenging for smaller comprehensive schools, because of the number of courses needed to cover a broader curriculum with comparatively fewer students. This is why schools have tended to get larger and also why many local authorities have organised secondary education into 11–16 schools, with the post-16 provision provided by Sixth Form colleges and Further Education Colleges. Comprehensive schools do not select their intake on the basis of academic achievement or aptitude, but there are demographic reasons why the attainment profiles of different schools vary considerably. In addition, government initiatives such as the City Technology Colleges and Specialist schools programmes have made the comprehensive ideal less certain.