If you bat on the left side of the plate, the ball is going to right field. Now move your tee to the front of home plate. This time, when you hit the ball it should head straight out to center field. Finally, place the tee on the inside edge of home plate. If you're batting right-handed, you're standing on the left side of home plate and the ball should be going to left field.
Young players have a hard time with outside pitches.
They want to go after the ball, so they reach out, which takes the strength out their swing.