Are there any chess books accessible for kids in the 9-11 age range that don't waste the first half of the book teaching how the pieces move, castling rules and en passant capture? I am expecting some basic principles of opening theory, strategies for the middle game (pawn structure, open files, long diagonals, doubled rooks, rook on 7th rank etc.), tactics (skewer, fork, discovered attack) and end game tips.
Winning Chess Strategy for Kids by Coakley is EXACTLY what you want.
Barely a few pages explaining basics. Then tons of practical content that even adults will find useful. Wastes no time in getting intermediate lessons in strategy/tactics presented in an astonishingly kid-friendly way. :)
Covers checkmates. If kids can't win a won game, they won't get good feedback even if they do everything else correctly. If they try to checkmate each other, everything else follows naturally (until they start to fall into endings, when it is time to pick up a good ending book).
A First Book of Morphy illustrates 30 basic principles described by grandmaster Fine in his "Chess the Easy Way" with games played by Morphy, the first chess genius and American champion. It's well suited for players rated under 1000.