Pretty sure it is not a rule. It is used in soccer so players keep their place on the field. Unless a kid is seriously injured I See no point in taking a knee. Sure it fine for mites but as things get more serious this is precious time for the opposing team to regroup. I have seen more kids milking a hit or fall than kids actually truly hurt.
Umm, that thread was like, a year ago. Why would you pull that forward if you had absolutely nothing of value to add? How did you even find it?