In 2007, Delaney carried out a study on footballers aged between 12 and 17 that showed they were half as likely to be concussed wearing headgear than without.
As Mike Wells writes at the Indianapolis Star, the NBA expressly warns that it might take days, if not weeks, for concussed players to be cleared to return.
You can find all sorts of advice about protection for your child in contact sports, and all sorts of laws and rules on when to bench a child who appears to be concussed.