It was my experience that Veterans, Physically handicapped, and foreign students were on the exempt billet.
Vet students were required to participate at least for first two years as were all (?) others - including athletes.
Having said that one of the most redass old army outfits that had year-to-year done very well in General Moore competition had a kid who had some motor problems and could not march without "bouncing" for the life of him His name was O'rell McDaniel. F-1 tolerated Orell's "problem" because he tried as hard as he could and was not otherwise a F...-up.
On the other hand, we were all aware of several guys who came to A&M thinking they were going to change things up or get their way as fish - particularly if they had JROTC backgrounds or were from the "north" (generally speaking). These guys did not last long - their personal effects were often found in the showers or out the window on the quad - no one knew how or what... but, they knew they did not conform and were invited to take Highway 6 - either way.
AAAAAAAAAAg - Air Force Aggie Architect and Hospital Administrator fm Amarillo, Altus, Austin, Arabia, Arkansas, Africa, Seoul, Bahrain, Amman, Kuwait, Iraq, Iran, Saudi, DFW-Fairview, Ramstein, San Antonio, Pentagon, OKC, JCAHO/JCR - '65, '69, '73 - A&M Letterman (ret).
Winston Churchill: “If you’re not a socialist in your twenties, you have no heart. But if you’re not a capitalist in your thirties, you have no mind.”