Did the Four Imams agree that a child under seven years old breaks the row?

The age of seven is the age of discernment, based on the Prophet's (peace be upon him) saying: "Command your children to pray when they are seven years old."

As for a boy who has not reached the age of discernment (under seven), his prayer is not valid, and it is not legislated for him to stand in the row. We are not aware of any disagreement among scholars regarding this, including the four Imams. Ibn Qudamah stated in Al-Mughni: "And whoever stands with him, such as a disbeliever or someone whose prayer is not valid other than those we have mentioned, his alignment (in the row) is not valid."