FWIW, my son's high school has them doing dumbbell bench press (not barbell) and dumbbell rows. Some sort of reverse wrist curl for the forearms/wrists. Medicine ball two-handed throws for the core/obliques . . . that's about it for upper body. Mostly they are focusing on lower body (deadlifts and squats).
In the interest of full disclosure, Elder, I have no idea if what they're doing in this regard in right or wrong -- just reporting what they have pitchers doing in the weight room.