Which puzzle for which age, and why

Each of the five puzzles asks for one skill and only works once a child has it: here is which skill goes with which puzzle.

Age ranges for puzzles are about one skill each, not about how bright a child is. Every type asks for a single thing, and it stops working when that thing is missing: the child does not find it hard, the child finds it impossible, and from across a classroom those look the same. What follows is which skill each of the five asks for, and roughly when it turns up.

Dot to dot, four to six. It asks for counting in sequence and nothing else, so the range of numbers is the difficulty: a child who counts confidently to 20 can do a 20 point picture, and counting to 100 is the usual ceiling of the last infant year. The picture is the reward and the marking scheme at once, because a number taken out of order shows up as a line straight across the drawing.

Word search, six to nine. It asks for letter recognition rather than reading: a child who can match the shape of a printed word against a grid can find it without being able to read it aloud. At that age keep to two directions, across and down, and put eight to twelve words in a 10x10 grid. Words running backwards are the step you add at nine or ten, because a reversed word cannot be read, only recognised.

Mazes, any age, because the only thing that changes is the size. Nothing has to be read and nothing has to be counted, so a 10x10 maze suits a five year old, 15x15 an eight year old, and 28x28 is ten quiet minutes for an adult. It is the one puzzle you can hand to a whole mixed group without sorting them first.

Crosswords, from eight. The clue is the barrier: the child has to read a sentence, hold it in mind, retrieve a word and write it one letter to a square, which is four things at the same time. Handed over too early, a crossword becomes a reading exercise with an obstacle attached to it. First crosswords work best with six to ten words the class has already met that week, so that the retrieval is the easy part.

Sudoku, from nine or ten. It is logic and not arithmetic, and the proof is that the digits are never added to anything: replace 1 to 9 with nine colours or nine animals and the puzzle is unchanged. That is why 4x4 grids with shapes work at six, while a 9x9 grid waits for the point where a child can hold a chain of two or three steps, of the form this square can only be a 7, because the 7 of this row has to be inside that block.

For a class with three years inside it, change the parameters and not the puzzle. The same word list gives a 10x10 grid with two directions to one group and a 15x15 with six directions and reversed words to another; the same maze gives 10x10 and 25x25. Everybody works on the same thing, everybody finishes at about the same time, and nobody is holding the baby version of what the child next to them has.