Very interesting topic....
Here in my corner of Ohio, I haven't run across MUCH problem with this type of overlap. But it disturbs me to read the low opinion that many posters have of high school coaches..... Maybe it is different by area, but I have been a head coach for 16 years and I find that 90% of the HS coaches in my area are very dedicated, caring well-versed and responsible coaches; they don't do it for the money, they do it because they love the game, love teaching baseball and, quite honestly, want to WIN.
Maybe this area of Ohio is different than many other places, but I don't see the "do nothing, know nothing" HS coaches that a lot of posters on here must run across. I do, however, see many select/summer/travel coaches who try to "sell" their program to potential players, and I think often tell those players some half-truths to get them to play on those teams.
That is the main concern I have for players on my school team. I admit that at the very beginning of my coaching career I tried to come on strong and get players to ONLY play on my summer team. But with age (hopefully) comes wisdom; and I realized that there were players who needed to play at a higher level than my summer team played.
So then it became a matter of trying to make sure that those players went to GOOD programs with GOOD coaching. And that is where I came across very bad behavior from coaches of summer programs: deceiving players and parents, poaching players, providing fancy promises and uniforms but not providing good coaching or honest adminstration of the team.
I, too, am concerned that the lessons learned in high school ball are not taught (often) in summer select programs. My thought is that if I DO start losing players to programs who convince them high school ball isn't relevant, I am better off without those players. I am a very big believer in the team concept, and if I have a player who is PRIMARILY concerned about getting exposure and advancing his own personal agenda, he won't be much of a team player (and, likely, neither will his parents). And I will be better off without him.
If that begins to happen around here, I will wish those players well, and move on without them, taking my "second tier" players with me and doing the best I can.
For those who believe that high school baseball is not very relevant for advancement, I guess I would say that I disagree with your assessment, but agree that you are absolutely entitled to your opinion and absolutely free to guide your son in the direction that you feel is best for him. Just make sure that he is going to a program that is going to look out for him the way I believe I do for all of my players. And go in with your eyes open about the program you are joining.