What the ruling says first
Fasting is not obligatory for a child before puberty. That is the starting point, and it matters that it is clear in the family's mind before any training plan: everything we do in these years is habituation and endearment, and its reward rests on intention, not on the count.
The Companions used to accustom their young children to fasting and would make them a toy of wool; if one of them cried from hunger, they gave it to him until it was time to break the fast. What stands out in that account is not compulsion but gentleness: the child takes part, is kept occupied, is helped to be patient — and is not left to suffer.
From this it follows that any training which turns into exhaustion or fear has missed its purpose. Nobody is rewarded for a child who faints at school.
The progression that works
Year one — present without fasting. The child joins suhoor and iftar, hears the call to prayer and waits for it, without being asked to abstain. The aim of this year is only that he grows used to the rhythm.
Year two — half a day on a day off. One or two days a week, on a day with no school, until noon. Then a celebrated iftar: "you fasted until noon, that is an achievement." The wording matters — an achievement, not half of one.
Year three — a full day now and then. Two or three days across the whole month, by his own choice. The child who chooses holds out; the child who is forced looks for an escape.
After that — expand as his strength allows. Some children fast the whole month at ten; others cannot manage it before twelve. The difference is normal, and no child should be measured against his brother or the neighbour's son.
Signs that require breaking the fast immediately
These are not matters of judgement. If any of these appear, breaking the fast is required, not merely permitted: marked pallor with cold extremities, dizziness or unsteadiness on standing, severe headache, vomiting, or unusual listlessness where he no longer responds as he normally does.
And tell him so in advance, clearly, before he starts: "if you feel dizzy, break your fast straight away and nobody will be angry." A child who fears your reaction will hide his exhaustion, and that is the real danger.
And if the child is diabetic, has any chronic condition, or is under his normal weight, the decision belongs to the doctor alone, not to the family.
Mistakes made in good faith
Comparison with siblings. "Your sister was fasting at your age" does not produce fasting; it produces aversion to the month, and to the sister along with it.
Announcing it to guests. It turns worship into performance, and makes next year's iftar an embarrassment rather than a permitted allowance.
Paying for each day fasted. It works for a week and then becomes a condition. Better a symbolic or shared reward at the end of the month than a daily price on fasting.
Lecturing while he is hungry. The hour before the call to prayer is the worst possible time for any teaching conversation. Postpone it until after iftar, when the child is ready to listen.
Frequently asked questions
Does a child have to make up the days he broke?
No. A child who is not yet obliged has nothing to make up, because fasting was not required of him in the first place. What he fasts in these years is training for which he is rewarded, and leaving it carries no consequence.
My daughter is nine and wants to fast the whole month. Should I allow it?
If her health is good, she eats well at suhoor and iftar and sleeps enough, there is no objection, with daily monitoring. Watch her energy and mood more closely than the number of days, and stop immediately at any sign of exhaustion.
How do I handle a child who fasts and then eats in secret?
Calmly, and without making a scene. He usually does this because he wants to please you and cannot finish the day. Lower the target to an openly declared half day, and the reason for hiding disappears at its root. The problem is in the level of expectation, not in the child's honesty.