Independent schools are often criticised for being elitist, and seen as lying outside the spirit of the state system. However, the treatment of the state sector as homogeneous in nature is difficult to support. The spectrum of state schools, their intake and performance, is enormous, going from "super selective", selective, right down to what Newsam referred to as "sub secondary modern". Although grammar schools are rare, some of them are highly selective, and state-funded boarding schools charge substantial fees, which may introduce further barriers to entry. Even comprehensive schools may be effectively selective because only wealthier families can afford to live in their catchment area; and it may be argued that the variation in performance of state schools is much wider than that between the better state and grammar schools and the independent sector. Smithers and Robinson's 2010 Sutton Trust commissioned study of social variation in comprehensive schools (excluding grammar schools) notes that "The 2,679 state comprehensive schools in England are highly socially segregated: the least deprived comprehensive in the country has 1 in 25 (4.2 per cent) of pupils with parents on income benefits compared with over 16 times as many (68.6 per cent) in the most deprived comprehensive"