The child who has reached puberty should be a part of the row and does not have to form a new row. Even small children must join the rows as well.

We know that in salah we are to straighten the rows and leave no spaces. Does it make a difference whether a child has reached the age of puberty for him to make a new row? In my masjid, we complete the rows, but the Imam orders the kids (12 under) to form a new row leaving a row in front of them empty and not completing the rows that have spaces in..