I went to a private high school that was absolutely loaded with tennis players. Tennis had absolutely nothing with my decision to go there, nor any of my teammates. We went there for the quality of the academics and the culture/tradition/reputation of the school, it just so happened we had the best of the best tennis players in the area all in one place. Not just tennis players, but other sports too.
The only time I have ever known of players choosing a high school specifically for sports is in the case of sports like hockey or lacrosse where not every school has a team.