The difficulties of being a student-athelete, especially when your sport isn't school supported

In most high schools, there is a policy toward student-athletes that is commonly called the 50-50 policy. That means that if you're involved in a school sport and another activity such as show choir which has after school events, you spend half of your time playing your sport, and half doing your other activity. This policy seems rather ineffective to me, since you will likely fall behind in both activities, but it is completely useless when it comes to club sports.
I play rugby for the Lawrence Claymores, a club team that is not even recognized by my school. As a result, I can't tell my choir director that I've got a game on the night of the concert so I can't go. His response would be, "Too bad. It's not a school sport. If you don't come I'm dropping you two letter grades." Fantastic, I know. I wish I could just tell him off and not go to the concert, but I know there's no satisfactory explanation I could give to my parents about how I managed to get a C in choir.This actually happened to me my freshmen year, so me and a friend who plays rugby and was in choir came up with a plan. We decided that we'd play for as long as we could and then rush to school for the concert. Of course, nothing really went as planned. We we're supposed to leave after about 20 minutes, but we got caught up in the game and our coach didn't really want us to leave, so we ended up leaving after 30 minutes. In the car, we were trying desperately to do our hair which was not in the best condition after having played rugby. We were supposed to have big, messy hair since we were singing that classic of classics, "Dancing Queen." It was an epic struggle, involving lots of hairspray, and gel. We arrived late and missed the opening number, but we did manage to escape the eye of our choir director, and so were not dropped two grades.
In my opinion, it's not really fair that schools do not allow any exceptions when it comes to club sports. For heaven's sake, my choir director let one girl skip a concert to go see Celtic Women. It seems to me that schools are rather prejudiced toward club sports, and are trying to give athletes a not so gentle nudge to participate in school sports instead, in the hopes that they will contribute to the school team and add to the school's glory. It seems unfair that athletes who participate in club sports are put at a disadvantage when it comes to their student life.