Ok, so here’s another layer to this. What are your thoughts on a coach giving a kid hitting lessons during the season? Not talking about coaching him up during BP. I’m talking about a full hitting lesson on their own time for which the coach charges the player.
On one hand, as a former HS coach, I couldn't imagine charging a kid in my own program for lessons. I also know that on the surface, this just looks wrong and seems a conflict of interest. In the past, I have argued adamantly on this side of the fence. I think this is where you will find most posters here sit as well.
On the other hand, i know of several coaches who rely on lessons as part of their off-season/supplementary income. So, if as example, a coach is part of a facility and has open enrollment for lessons and a kid in his program signs up, is the coach expected to decline or not charge the kid for that slot where he otherwise would be paid for his services? I've come around to believing, while it's not something I could do, its not that cut-and-dry for everyone.
From a timing standpoint, however, I think your "during the season" scenario factors in. That adds to the conflict of interest argument and is worse from a perception standpoint. I never refused a player any individual extra work before/after practice if asked.