Short answer
In the Hanafi school the order is men, then boys, then women. If there is only one boy, he stands in the men's row. A child standing in the row does not break it, and many scholars today prefer to spread children among adults so they behave. A boy praying alone with an adult stands on his right.
The sunnah order of rows is adult men, then boys who have not reached puberty, then women. A single boy joins the men's row. A child of understanding standing beside adults does not harm their prayer or the row.
The four schools agree on this.
Explanation
The Prophet ﷺ said: let those of mature understanding stand closest to me, then those after them. Anas reported praying behind the Prophet ﷺ with an orphan boy beside him in one row, and his grandmother behind them. From these reports the four schools agree on the basic order: men, then boys, then women.
Practical points:
- One child: he stands in the men's row, as Anas and the orphan did.
- Several children: the classical order puts them in a row behind the men. Many scholars today say that where a separate children's row leads to play and noise, spreading them among their fathers is better, and the row stays valid.
- Moving children back: do not pull a child out of the first row in a way that hurts or humiliates them. Gentle guidance works better.
- Father and son alone: the son stands on the father's right, level with him, as Ibn Abbas did with the Prophet ﷺ.
- Girls: stand with the women.
Children too young to pray properly are better kept with a parent, outside the rows. See children in the mosque and when children start praying. For the prayer itself, see how to pray.
The evidence
Sahih Muslim 432
Sahih... ليلني منكم أولو الأحلام والنهى ثم الذين يلونهم ...
"Let those of you who are mature and wise stand closest to me, then those who come after them."
The basis for the order of rows.
Sahih al-Bukhari 380
Sahih... وصففت واليتيم وراءه والعجوز من ورائنا ...
"The orphan and I lined up behind him, and the old woman stood behind us."
A boy stands in a row with others, and women behind.
Sahih al-Bukhari 699
Sahih... فأخذ برأسي فأقامني عن يمينه ...
"He took me by my head and placed me on his right."
A single follower, even a boy, stands on the imam's right.
Where the ruling is recorded
- al-Hidaya, Kitab al-Salah, chapter on the imamate. The order of rows: men, boys, then women.
- Radd al-Muhtar (Ibn Abidin), Kitab al-Salah, chapter on the imamate. A single boy joins the men's row.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.