I taught my kid to hit outside pitches to opposite field, middle pitches to center field and inside pitches to left field. (He is right-handed). I also taught him I didn't care what type of pitch, FB, curve, change, etc. that was the approach.
Told him, though, most common approach to high school is outside, therefore must get good on outside of plate. Also told him he could be a .350 high school hitter if he just swung at middle pitches because pitchers miss.
I think the coach needs to read this website. Many great hitting coaches here. If I coached ping pong, which I know little about, I would at least research it, read all the books I could find and seek advice. How do we have so many coaches that are so inept? I know most are not but how can a coach that is a head coach in any sport not go get the info in this day and age?