Coach and the Parents
All conversations between a coach and a parent should be considered privileged communication. When parents talk with the coach about a specific concern they have for their child, it often begins with, "Don't say anything to (my child) but..." And naturally, the parent expects that to be honored, even if it's not spoken.
Most of these conversations come about due to a lack of playing time, regarding a specific position, or filling a certain spot in the batting order. As parents, the likely want to know why, and it's understandable. First, you should have already communicated this to the player. But, if that hasn't happened, it should be the next conversation you have with him or her.
Coaches disagree on the topic of justifying their decisions to parents or not. I believe a coach should be able to justify his or her position to the parents - he or she should have a good reason for the decision and should be able to verbalize that. Once the explanation has taken place, if the parent continues to push, the conversation can end.
A good idea is to involve your parents in your program as much as possible, ensuring to help them understand exactly what you wish to accomplish, and why. Pay special attention to the families of the substitute players as they're likely the ones with growing frustration.
Coach and the Student
Students sometimes feel a need to confide in another adult, other than their parents. This is often their coach. While you may be flattered that the student chose you, understand this comes with great responsibility. The topic of the conversation is sometimes one that the athlete wishes for the coach to keep away from their parents. There is a great danger in agreeing not to tell the parents about the conversation. If you agree = rock and a hard place.
A safe approach to the opening statement, "Don't tell my mom or dad but..." is to say, "I can't promise that. Let's talk about it and we'll figure out the best course of action." Much safer for you, and, if the kid approached you in the first place, he or she is likely to open up to you anyway.
The "every" Concept
Every parent wants to see their kid play every minute of every game and for the team to win every game.
This is a line of communication that cannot be used enough, especially when more than one team or organization uses the same field or gym. The specifications will vary from organization to organization as to the intricacies of facility usage, but one rule remains constant - communication early and often with the facility manager and other coaches to ensure your practice time or game isn't the recipient of the double-booking.
One of the most difficult, and important tasks for a coach to learn is how to deal with critics - the quarterback in the stands, the backstop dad, and the coffee shop coaches. Regardless of the size of the community, the size of the team, or the ages of the players, someone on the sidelines thinks they can do a better job than the current coach. Even when the team is winning, someone will complain because their kid should have gotten into the game sooner, or you shouldn't have run the ball on 3rd and 1, or you waited too long to foul when down by 4 with under a minute to go. I've heard critics say the coach ran up the score, some say the score wasn't a high enough margin. I've even listened to a parent complain that the football team came out of the halftime locker room too early as she was still in line for the concession stand.
The point of all of this is for you, the coach, to understand that people will always find something to pick apart, and the coach who keeps an ear to all of these "experts" is in trouble. If you please 75% of the people, you're doing better than most.