Multisport, great question. Don't be surprised that many of us who grew up around baseball wonder the same thing. I'll tell you what I did. I looked around and asked around, which hitting coach in the area is the best? This is an impossible question to answer. But which hitting coach is a magnet for the best HS players, college committed players, MiLB players who come back in the off season? Not what organization, but what coach/instructor? This you can find out.
Also, I agree with Cabbage and Trust 100%. My son started with his coach when he was 13 (he's a senior in HS now). Weekly hitting lessons in winter and spring (football in the fall). The emphasis was always on what it takes to hit great pitching - as Cabbage said, most kids can hit poor or average pitching so "hitting well" may mean nothing at all to his development. It takes time to develop great mechanics and IMO you want great mechanics when you pick up a BBCOR bat on a big field, otherwise you'll find the bench and have an uphill battle getting playing time.