Have you ever considered that pushing your child toward something (i.e., a SA) can lead to exactly the opposite outcome?
2012mom is dead on. As a SA grad, I think we all have a natural tendency to wish our sons / daughters could go through the same experience. I secretly wanted my kids to attend a SA from early on and definitely had to exersize constraint at times to not come on too strong.
We are close to Annapolis, so I exposed them to the SA atmosphere through trips to USNA football games / driving around the yard / sea stories,etc. Being careful not to push one way or the other, but letting them observe and make the decision. Long story short....my daughter figured out that it definitely was not for her. She went on to graduate from 4-year liberal arts college...now successful and gainfully employed. Son, on the other hand, was attracted to it...attended summer seminars at both USMA / USNA. Ultimately decided on USMA where he is currently a yearling.
Bottom line - all you can do is give them the resources / exposure /nurturing and let them decide!