First pitches are meant to be fastballs for strike, not always works that way
There is usually a sequence of pitches, your sons coach should explain this to him. The sequence may become too difficult (curves, off speed), but the first is ususally the plain old fastball.
If the batter sits on the first pitch and misses, he's already down in the count.
The best hitters are able to recognize where the pitch is going (what type of pitch) after the release point, they might be able to afford to sit on the ball, but most can't.
In college, you don't play if you sit waiting for the perfect pitch to arrive at the plate.
Mine is not a batter, a pitcher who throws (or tries) his first pitch a fastball.
JMO