I agree with Sandman, that most young hitters hit to the opposite field due to timing (or lack of) rather than purpose.
I will qualify it though. I believe that a young hitter can become at least "aware" of how it feels to hit to the opposite field given enough batting practice.
Many of you have seen my sons "uppercut" swing that he has always had naturally and a swing that he has worked on for the past few years. Well, after Cooperstown this past June, he has worked on "nothing" but line drive hitting and hitting to the opposite field on outside pitches.
Our goal was to improve his batting average because many of those deep fly balls that used to result in doubles now simply get caught.
He hits 200 bp pitches or 200 front-toss pitches with "full effort" each session 2 or 3 times a week. It is easier for me to control the strike zone with front-toss, particularly for opposite field drills but regular bp is necessary to keep his timing.
If he pops up, fouls or hits a deep fly ball he runs a pole! He ran a lot of poles in June and July! He is becoming extremely effective hitting powerful line shots. He is less effective on the outside pitches to the opposite field but he is improving. I firmly believe that younger hitters can learn to go with the pitch if they see enough pitches. An added benefit for my son is the running!