It is a concern for parents, my 5 year old son plays soccer as it develops good coordination, team work and kicking skills. I don't practice headers with him and don't really want him playing any full contact sports including Rugby until he is older, if he chooses to.
I think you will find heading practice and heading in games is banned at local park level until I think U 12.
Personal story, I was 21 and playing both league and union.
Union on Saturday and League on Sundays.
I played league at a semi professional level in the Parramatta competition and we had teams like Wentworthville, Guildford etc and all had leagues clubs to support. My team was Guildford we had the highest post in Australia.
Was playing Mount Pritchard at their home ground and they had a cricket pitch in the centre that was rock hard.
I always played as a half and in these days league scrums were contested. The side that caused the scrum got the loose head and they other side got to feed the scrum, 4 tackle rule as a time frame.
Scrum just in there half, they feed the scrum, there half got a bad bounce out of the scrum I darted around picked up the loose ball and there half grabbed my arm and was holding me he was on the ground I was standing, so turned and called my lock to come thu and take a pass from me.
There lock a former ARL player of some note [for foul play] I think also played for the Kangaroo's was there lock and he broke from the scrum, lifted his shoulder into my chin and threw me in the air then back slammed me head backwards into the cricket pitch and the last thing I recall was he came crashing over with an forearm to my head.
Hard to believe but I played on and somehow drove home. I was dizzy for days and still felt funny months latter. My Dad pulled me aside and after a long chat I quit playing both league and union as I was just to small.
I gotta say looking back on it now it was one of the smartest decisions I ever made.
Medical advise I have received [thats how I know about the no heading until up to U12] is that child brains until you are a teens are less protected and can be damaged.
It is a real issue, and also they are finding out that women's breasts can be damaged with constant big knocks and I have been told it could become as big an issue a head knocks unless sporting codes take some action.