No matter the ages of players or the experience of the baseball coach, some hitting instruction absolutes exist that all must know and apply. The ironic part of hitting instruction, the more one knows, the more one realizes there is to learn. That fact attests to the difficulty of perfecting the baseball swing, and of coaching hitting.
Of the over 65,000 baseball lessons I have given over the years, I know there is some percentage of lessons that did not work. I don't believe that was because of what I was teaching. it had to do with little-known factors of coaching hitting that took me years and many lessons to comprehend.