From reading tons of information out on the web and posts here, the majority of prep school appointments are reserved for "a red shirt" year for the D1 athletes and a method to help back fill the required quotas. If you fall in either category you have a great shot at the prep route. If you do not fall into either of those categories , a good starting point would a 32+ ACT and 4.0+ GPA, below that is a very steep uphill battle.
The majority of prep school slots are not reserved for D1 athletes to have a red shirt year. Almost 25% of the prep school; about 50-55 are prior enlisted. And for what it's worth, the main reason the prep school was established, was for prior enlisted. As for the rest, you will see every makeup of students you can imagine. White, Black, hispanic, men, women, athletes and non-athletes.
Do some students at the prep school happen to be potential D1 athletes at the academy? Yes; of course. But considering that the academy sponsors 29 intercollegiate teams, and 27 of them are sanctioned NCAA teams, (More than just about ANY university in the country) and considering that 25% / 1000+/- cadets are intercollegiate athletes (Physical fitness is paramount and one of the most important attributes in the military); then it's quite likely that some at the prep school are going to be potential D1 athletes. But they aren't the majority.
The prep school is for applicants the academy feels has an outstanding application, except in an area that needs work on. Usually academics or leadership. There's an outstanding chance, that if you had a 32ACT and 4.0gpa, you wouldn't be offered the prep school. You obviously don't need help in academics.
The academy and the military wants a cadet corp that is as diverse and representative of the "Enlisted Corp" that they are going to be leading in the near future. Every attribute that a cadet brings to the academy contributes. Just like the academy was looking for the "WHOLE PERSON CONCEPT" when they reviewed your application; the same goes for the class itself. They want the "WHOLE CLASS CONCEPT". They want a class that makes for a well rounded class. A class representing every attribute imaginable. White, Black, women, men, rich, poor, athlete, band, JrROTC, CAP, Spanish club, inner city, suburb, farm and ranch, brainiacs, work experience, single parent, first in family to go to college, etc. You name the attribute, the academy wants that as part of the class. Why??????????? BECAUSE THOSE ARE THE ATTRIBUTES OF THE ENLISTED CORP they are going to lead.
So yes, the prep school has some students who will play Intercollegiate sports. Well guess what? 25% of the academy is going to play Intercollegiate sports. And yes, the prep school will have minorities in it. So does the academy and the real military. But the prep school is not a place to provide a "RED SHIRT" year for athletes, or for unqualified minorities so they can prep them to qualify for the academy. The #1 purpose of the prep school; is for active duty airmen applying to the academy. The rest of the slots, are for individuals that have an excellent application, minus an area such as academics or leadership, that the academy feels has great potential. And FWIW; only about 75-80% of those who complete the prep school, receive an appointment to the academy.