PUHD,
I agree with the repetition part of your comment. Repeating a properly taught swing thousands of times over the winter is invaluable.
Many kids in our area train at the same academy as my son. When you go to a high school game around here you can spot these kids with their first swing.
RJM,
you are correct about opening academies. Seems one or two opens every year around here. One or two closes every year also!