What it teaches
What actually makes a password hard to guess. Length beats punctuation: a long password of plain words is harder than a short one full of symbols, and children are usually taught the opposite — that a password is strong because it has a % in it.
It also names the passwords that are guessed first, which is more useful than any rule: 1234, qwerty, the word "password", this year, and your own name.
How it works
Two passwords appear and the child picks the stronger. The reason is given once the answer is right, and it is a reason rather than a rule — "keys in a row on the keyboard are the second thing tried".
What to look for
The pairs are chosen so the clever-looking one loses. That is deliberate and it is the misconception worth breaking.
Three plain words stuck together is a genuinely good password and a child can remember one. That is worth saying at the same time.