*A person educated at Eton (or who attended Eton) becomes an Old Etonian on Leaving; similarly a person educated at Harrow an Old Harrowian; a person educated at Winchester an Old Wykehamist; a person (like me) educated at Shrewsbury an Old Salopian; and at Chaterhouse an Old Carthusian.  The fact that articles may refer to them as educated at foo college, not as an Old Fooian should make no difference.  These are major public schools and these terms are (or should be) well-known.  I believe we should retain the denonyms for these, but that this needs to be limited to a relatively small number of the most major public schools.  For minor public schools, grammar school, and comprehensives, we should not.  The WP consensus is that categories should be renamed to "People educated at foo" where:  
 #ambiguity arises;  
 #the demonym for school is obscure; or  
 #the school has few notable old boys, so that the old fooian term is obscure.