ھ is not a regular consonant. It is an aspiration marker, the spelling device that turns plain k into kh, plain p into ph, plain t into th, and so on. Urdu has two he letters: ہ choti he is the consonant that makes the h sound on its own, and ھ do-chashmi he is the marker glued to other consonants. Children often confuse them because both look loosely h-shaped. The fastest way to fix this is the word-pair drill: کھانا food versus کہانا a story; the first uses ھ, the second uses ہ. Whenever your child writes a kh, ph, th, ch, bh, dh, jh, gh sound, the correct second letter is always do-chashmi ھ.

ھ is small but it is the letter that puts the breath into Urdu words. کھانا without it is a story, پھول without it has no scent. Tell your child this is the letter that carries air across the page.