Like some schools, there are several industrial teams that also emphisise baseball. These leagues act like an independent minor league system. Toyota, Nihon Seimei (life insurance), Nihon Sekiyu (oil), and several others tend to "educate" a large number of pros.
If you have more concrete questions, you may want to ask radio personality and Pro Yakyu fan Michiyo Ishida about high school and college ball's influence. Keep in mind, though, she's very busy and may not be able to reply right away. The less vague the question, the easier to get a reply.
Well, I hope this helps you get started. I'm sure that Google searches on key words like "Koshien" will turn up more information. Gambare!
This is a site about Pro Yakyu (Japanese Baseball), not about who the next player to go over to MLB is. It's a community of Pro Yakyu fans who have come together to share their knowledge and opinions with the world. It's a place to follow teams and individuals playing baseball in Japan (and Asia), and to learn about Japanese (and Asian) culture through baseball.
It is my sincere hope that once you learn a bit about what we're about here that you will join the community of contributors.
Michael Westbay
(aka westbaystars)
Founder
Thanks to anyone who can answer this.
Jerry