Why b and d are so hard
Everything a small child has ever met is the same object when it faces the other way. A cup turned round is still a cup; a dog seen from the left is the same dog seen from the right. The brain is built to ignore mirror flips, because in the physical world they never matter.
Then reading arrives and breaks the rule. A b and a d are the same SHAPE mirrored, and now they are two different things with two different sounds. Learning to READ means partly unlearning something the visual system does automatically, and brain scans of adults who learned to read late show the change happening. Reversing letters at five is not a warning sign. It is the old rule, still working.
Reciting numbers is not counting
A three-year-old who can chant one to ten sounds like they can count, and usually cannot. Ask that child to hand you three bricks from a pile and they will very often grab a fistful, because the last word of the chant has not yet connected to the question how many.
Psychologists test it exactly that way, and children pass it in stages: first they can give one, then two, then three, and only after a year or so does the penny drop for every NUMBER at once. Counting aloud to SEVEN or EIGHT and knowing what seven means are separate achievements, and the gap between them is completely normal.
Rhyme predicts reading better than almost anything
Of all the things you can measure in a four-year-old, one of the strongest signals of how easily they will learn to read is whether they can hear that cat and hat end the same way. It beats knowing the ALPHABET, and it beats how many words they know.
The reason is that reading English means mapping sounds onto letters, and a child who cannot yet hear a word breaking into parts has nothing to map. Nursery rhymes, silly songs and deliberately awful jokes are doing the groundwork, which is a comfortable thing to know when the same rhyme is demanded for the ninth time.
Everything here is the same idea
COLOR, SHAPE, NUMBER and LETTER look like four separate topics on a nursery wall. Underneath they are one: a mark or a sound standing in for something that is not there.
The squiggle 7 is not seven of anything. The word RED is not red. A CIRCLE drawn on paper is a decision to treat a wobbly ring of pencil as a perfect one. A child who grasps that symbols stand for things has the key to reading, arithmetic, music, maps and money — and every sub-topic here is another rehearsal of it.
What is in the grid
Colours to start with — RED, BLUE, YELLOW and GREEN — then the shapes, a CIRCLE, a SQUARE, a TRIANGLE and a STAR, then SEVEN and EIGHT, the ALPHABET, and the words for what you are doing: COUNT, SPELL, MATCH, LEARN, READ and WRITE.
PATTERN deserves its own mention. Spotting that red-blue-red-blue carries on with red is the first piece of algebra anybody ever does, and it turns up again in spelling, in times tables and in music. A word search is quietly the same exercise: scanning a field of noise until the shape you are looking for stands out of it.