Children in Masjids

We notice that amongst sub continent managed masjids, there is a general dislike of including small/pre-pubescent children in the rows for salat, these children are told to form there own row. Is there any grounding in the shariah for this? Or can children pray in the same row as adults? Where has this ruling of banning children to the back derived from?

Assalamu alaykum

In the name of Allah, the Inspirer of truth.

1. It is recommended that when there are a number of children they should perform the prayer in a row of their own behind the adult men.

Allama Shurunbulali has narrated a hadith from Abu Malik al-Ash'ari that Rasulullah Sallallahu alayhi wasallam lead the prayer while having the adult men stand close to him, and forming the children's row behind them...

However, if there is not a group of children then they will be integrated into the rows of the men. [Radd al-Muhtar, Maraqi 'l-Falah]

Abdur-Rahman ibn Yusuf