I think it masssively depends on the SEN of the child - It is quite right that children should be educated with their peers where this is possible - by physical adaptations to schools, specialist equipment etc. Alos where it might mean some adjustments to the curriculum (everyone not having to do 8 GCSEs whether it meets their needs or not for instance). It also depends on the school - a primary school or small secondary school might meet the needs of a child on the AS where an enormous great warehouse of a secondary wouldn't. Inclusion, properly done with the facilities in mainstream to meet the needs of all children is very expensive and is therefore very rarely (never?) done properly.