I don't have any numbers to back up my thoughts about pitching in the summer being better...I just know what I've seen. Keep in mind that my son's HS schedule is no where close to some of the top teams in Ohio....and certainly not up to the schedules of teams in the South. We are a fairly small school...and most of the schools we play are our size or even smaller.
I guess I would look at opposing pitchers the same way I look at my son when he pitches...with regard to HS vs Summer. In HS, he feels like he has to strike out or overpower the hitters because he's afraid his defense won't be able to help him out. He relies more on curveballs hoping to get swinging strikes...as opposed to just throwing strikes and letting the hitter put it in play and his defense work. Obviously this attitude has got to result in fewer strikes as he is much more of a "thrower" in these situations...than he is a "pitcher". In the summer he has a completely different approach on the mound...he's willing to throw strikes, let kids swing and let his defense help him out...and he doesn't necessarily try to strike out everyone...meaning less curveballs in the dirt, wild pitches or passed balls. I'm thinking that that may be a big part of why summer pitching is (or at least seems to be) better than HS with regard to strike %....maybe it's real, maybe not....I guess I really have no way to say for sure