I would be wary of a BJJ program that had kids practicing submissions on each other while free training when they are under the age of 7. The kids practice doing arm bars on us all the time but know that they are not allowed to use them against each other until they get to the older class. Is better for them because they learn how to move and transition first. I know many members of The Gracie family and this is how they been doing it for years.You inadvertently answered a question a didn't ask because this is a taekwando post. But my concern with BJJ as there Gracie Kids program that will take kids as early as 3 was submissions. I didn't think my kid would realize that he needed to tap and get hurt.