This is a recent example of a theme, but I could show you very many more from my database.
Many children only seem to know one checkmate: that which is often, under the influence of Mike Basman, known as the Lawn Mower.
You know the drill: checkmate with two rooks or queen and rook on the side of the board.
Black, a strong player who does well competing against adults, won several pawns in the middle game and has just queened one of them in the ending. In a 30 minute game, neither player has too much time left.
Rather than looking for the quickest finish, he, as they always do, plans to use his queen and rook to checkmate White on the a-file.
If you’re good at this sort of thing you’ll spot the quickest finish: 45.. Qb4+ when 46. Ke5 runs into Re2# and 46. Ke3 and Kd3 are both met by Qd2#. Instead he put his rook in place: 45.. Re2. Next move he’ll check on the d-file and gradually force the king to the a-file, just like mowing the lawn one strip at a time.
White played 46. Rf4 and again Black had a mate in two, this time rather easier to find as there’s only one variation: 46.. Qb4+ 47. Kd3 Qd2#. But instead he followed his predetermined plan: 46.. Qd1+. Now after Kc5 White can hang on for a few more moves, but instead he played 47. Kc3, allowing a mate in 1 with Qd2#, a mate in 2 with Qb3+ or a mate in 3 with Qe1+. White was intent on following his plan, though, so played 47.. Rc1+ 48. Kb4 Qb1+ 49. Ka5, when he realised it was not quite so simple as his own a-pawn was in the way.
At this point Black stopped notating, so I don’t know how many moves it took him to finish off his opponent. My computer tells me it’s mate in 4.
Now we can hardly blame Black for his inefficiency here. You may well agree that it’s better to play ten quick moves to reach a familiar checkmate than to spend a long time looking for a quicker win. Even better, though is to play one or two quick moves to reach a checkmate. If we ran proper structured chess tuition incorporating regular tactics training they’d be able to do that. If you look at, for example the Steps Method, or Laszlo Polgar’s big tactics book, you’ll find hundreds of checkmate puzzles.
How many juniors actually do tactics training of this nature on a regular basis? In my part of the world, some, but not very many. Encouraging children to spend 10 minutes or so every day solving puzzles, and there are a number of website where you can do this for free as well as many excellent books, will do much to increase playing strength.