An Atlas of English Dialects. Second edition
By Clive Upton and JDA Widdowson
It's a sign of the quality of this book that you want to keep arguing with it. It says that in Yorkshire they call coal dust "slack", whereas I think they are two different things: "slack" is little bits, but "dust" is, well, dust. We 'ad a coil 'oil in Sheffield, so I ought to know.
That sort of niggle apart, to provide a book of maps showing ways in which common words and expressions are variously rendered from place to place is a fascinating project. You do need to approach it by understanding that boundaries can't be as sharp as those on the maps, and that the finest details - of the differences between Sheffield and Barnsley, for example - are almost beyond analysis. Given all that, this is a book for browsing, learning from and arguing about, and in school it will remind children of a richness in the language that deserves to be studied and preserved.