Hm, 2.5 miles are 4 kilometers - perfectly walk- and bikeable. Any teenager easily can do that, over here, they would. I do not see the issue, especially since it will not hit everyone.

Alternatively, and this may be a radical idea: If your town is five kilometers across, with a uniform distribution of population: Why not have two, or three smaller schools, evenly distributed? A similar-sized German city (taking Öhringen, ~25.000 citizens, which also follows the 'almost a circle' rule, as an example here) has six highschools (which also take in students from neighboring villages)...