Kids with great pitch selection get much better results than those who are at the two extremes (swing at almost everything, or looking for a walk). My son is someone who is great at getting contact and can easily do it even when the ball is a foot or more out of the strike zone. Whenever his confidence as a hitter goes way up, he has a tendency to become ultra-aggressive at the plate swinging at pitches more than half a foot out of the trike zone and putting the balls weakly into play, or popping them up. Then we have to go through a several week correction process where he reigns it back it. Been through this several times.
Funny at bat during BP two weeks ago - I threw a pitch to him that was going right at him - maybe even a little behind him. He jumped back over 3 feet, swings, and pulls it weakly to 1st base . . .