Well yeah, if they can adjust. Been doing it a while myself as a player and at different age groups and depending on the batter rather than the pitcher.
My son, he's nine and hasn't learned to adjust, so I move him all over the place based off of speed so he can be in rhythm and smash the ball. One of our other coaches that teaches kids preaches back of the box to see the ball, but it does absolutely zero when they don't understand the concept of weight back and all you get are lazy dinks and outs at first. Can tell them till you're blue in the face, just depends on how they react. I am an honest believer as well that unless you understand, that extra millisecond isn't helping as much until you get older and your brain comprehends what you're looking for. Any extra time helps in theory, but it isn't a night and day difference unless you know how to use it and see it.