Thanks for the debate Con, I accept. I would like to suggest that by girls and boys you mean females and males. If this is not the case, please clarify in the following round. I say this to ensure that the scale of the topic covers all age groups. I also propose that we define a "competitive sport" as an activity involving physical exertion and skill, in which two or more persons compete. Looking forward to an interesting debate.
I contend that girls should be able to play sports with boys, in the interest of fairness and equality. Although many existing sports organizations have a predominate race, the draft is desegregated and based solely on skill. So must it be with gender. To claim that sports should be segregated by gender, my opponent must show some inherent weakness in women- one that men do not posses, or he must present some dynamic and compelling evidence that provides moral reason for breaching equality in such a universal way. He also must show that this weakness exists only in women between the ages of 12-18, or is exhibited in a much more profound way during those ages.
Further, I do not accept my opponents stipulation of "physical sports". Contact or non, competitive sports are competitive sports. My definition was purely a splice between the technical definitions of sports and competitive.
Until Con presents compelling evidence for this mandatory inequality, we must concede that sports must not be segregated by gender.