Concussions have become and increasingly legitimate concern in athletics and there has been a lot of press given to this of late, particularly in the NFL.
That said, there are concerns in casual sports as regards the potential for head injuries of consequence, and toward that end, I have two links for you that are useful for evaluating someone with a head injury, whether it’s a child or an adult.
These forms allow one to do a formal assesment for concussion after an injury. They are rather extensive, and for that reason may not be practical, but if you take a look at them, they will provide a framework for you to understand what is being evaluated and what things to look for in such situations.