Your smartphone may be able to tell you the answer. An app called Concussion Recognition and Response (CRR) walks you through a checklist of signs and symptoms to help determine whether an athlete should be removed from play and be examined by a doctor. The app will also save relevant information so it can be shared with medical personnel, and let parents continue to observe and record symptoms in the days and weeks following a suspected concussion.
The app also provides guidance on how an athlete should gradually return to play. It costs $3.99 and is available for iOS and Android. You can also read more about concussions here, including which sports have the highest risks.