I know this from personal experience: my daughter has had three concussions (not all sports-related) since last May, and is only now returning to play.
She experienced months of headaches, inability to concentrate, sensitivity to light, and compromised balance. She missed over 60 days of school since last May.
We were fortunate enough to receive treatment through Dr. Vince Schaller's concussion network in New Castle County and the Sports Medicine Center at Temple through Dr. Peter Torg.
But Alexis is still on three meds to keep the headaches from returning, regularize her sleep patterns, and assist with her balance. All of the docs (including the Temple neurologist we saw on consult) tell us she will be dealing with the headaches until she is 19 or 20 (she is 17 now).
The major concussion that started this all was a fluke: she is a soccer keeper and in ten years of play at that position had never been hit in the face with a ball from a close-up kick.
A lot of people have criticized us for allowing her back on the field; I think they would prefer her wrapped in bubble wrap.
The problem is, for Alexis and a lot of other kids, sports is a large part of their reason for striving, for keeping themselves together, for enjoying themselves. She is a competitor who (ironically) only does her best in school when half her time is taken up by games and practice.
Life is about realistically and responsibly managing risk. There has always been a risk every time she steps on the field (she's broken fingers and been covered with abrasions many times), and they don't categorize soccer as a "collision" sport for nothing.
On the other hand, parents need to take the time to learn about the symptoms and seriousness of concussions, and to realize that (a) having a baseline IMPACT test before practice or play is always a good idea; (b) that ALL head trauma should be assessed by not only a medical professional but one with experience and training in concussions; and (c) that the priority is NOT immediate return to sports to "play through" anything, but to be sure that the child is symptom-free for an extended period before she or he steps even onto the practice field again.
Again: if you have student athletes in your family, please take the time to research this.