Per the NCAA Clearinghouse, you have to qualify for both DI and DII.
In answer to your question Baseball is Life,, I can only speak on behalf of basketball. As a former coach for an elite high school basketball travel team, attending a prep school or post-graduate school was the preferred route for several of my players. These schools recruit nationally, and seek only the elite players. By attending these prep or post-graduate schools, it allowed the athlete to AVOID LOSING COLLEGE ELIGIBILITY. However, the NCAA is starting to clamp down on these schools in an effort to stop the so-called “diploma mills” and are taking aim at prep schools created in the past 10-15 years at which athletes could take the core courses they needed. In order to retain four years of college eligibility, athletes in danger of not completing the 14 core courses had taken two routes: reclassification, essentially repeating a grade in high school; and going to prep school for a post-graduate year, during which players often loaded up on core courses.
This past April, the NCAA approved a new bylaw. From what I read, the new rule requires athletes to pass all but one of the required 14 high school core courses in eight semesters. The number of core courses will increase to 16 beginning in 2008. Athletes still can attend prep school, but only to increase their SAT or ACT scores or to take one additional core course. Perhaps some others on the HSBBW can elaborate on this.
With the passage of this new law, I expect the JUCO route will be the preferred destination for athletes who fail to qualify academically. Even though it means they will only have two years of college eligibility left after transferring to a four-year school, it becomes a motivating factor: Get it going in the classroom!
I believe the timeline for submitting applications to many of these prep and post-graduate schools are very similar to 4-year colleges and universities. I sincerely wish you and your son the best of luck in his academic and athletic pursuits.