I don't recall ever having a conversation about baseball with my son that started out with "Now that you are in HS....."
The expectations haven't changed since he decided that he wanted to play baseball competitively. Work to get better, stay humble and don't forget to have some fun. If he didn't know how to respect authority, how to practice, be a good teammate....etc, it was going to be a little late to drop that on him just because he was entering HS. Baseball is hard enough on its own merits, why give them something else to worry about as a freshman? It won't change ability.