Sure, some of that occurs. But having effective open enrollment subject to capacity makes it extremely difficult to police. Therefore, it is easy to get away with. Over the past 25 years which is about the length of time I have watched area football, the concentration of talent has exploded as rule changes made it easy to go wherever one wished.
Look, to me there are legitimate reasons for kids to attend school out of zone. Three that come readily to mind are: 1. Attendance at a Magnet program related to the kid's career interests; 2. In a situation where a kid has already completed at least 2 years of high school when a new school opens up. In this situation, I feel he/she should be allowed to complete high school where they started. 3. A situation where upper level courses are not readily available to a student that that demonstrates the academic capacity to do them.
A fourth situation that relates directly to athletics that I would consider legitimate, is if the zoned school does not offer the sport that the student wants to participate in.
Aside from the above, I don't believe that kids should be allowed to transfer willy nilly. Athletics in general would fall into the illegitimate category unless the family actually moved into the other school zone.