how the boys appearance suggest that they were no longer english school boys

The boys lose any resemblance to british school boys as the book progresses. Golding even names Chapter 4 "Painted Faces and Long Hair". Certainly the painted faces free the boys from their earlier identities in their old world. In Jack's case the mask helps unleash his inner socio-path. By the end of the book Golding has stopped calling them boys; he calls them savages. In a final attempt to appear to civility, Ralph suggests they comb their hair and wash up to somehow remind the boys of who they used to be. This, of course, doesn't work. The boys have become accustomed to the grime and trinkets that define them as savages. They have become the opposite of the "civilized" British school-boy.