In Chapter 5 of "Lord of the Flies", when Percival remembers his name and address but not his telephone number, what does this show?

I agree with both answers as provided above.

Has anyone stopped to wonder why Golding provides "St. Anthony's" as the name of the school Percival attended? 

I think this may have some symbolic importance to the story as well, though I am definately not an expert. 

If you were to do a search for Saint Anthony, you may find that he is a patron saint for of many things, including epilepsy.

In works of art, St Anthony is usually portrayed with 4 symbols: Tau, a bell, a pig, and fire or flames.