I can't think of another sport where I've heard of closed practice at this level. We encourage parents to help and I have even said a few comments to parents about talking to there kids at practice. I'm proud to say all my coaches coach everyone in the room. One of my main goals was to advance the skill level of everyone in the room (no kid left behind). If your having a closed practice it's beacuse one of two things. One the parents are coaching from the stands or two people are complaining about there kid getting equal coaching time.
In Luellens case I could understand his opinion. There wrestling room is fairly small and the mats go from wall to wall, not really much room for parents. Parents are also in close contact with there children which ads to the problem. I think club directors and coaches should talk to there parents before making this decision to close practice. Let them know that sideline coaching isn't permitted and make your parents feel welcomed in practice as long as they follow the rules. Make the rules clear and follow through. Coach all the kids in the room and if your kid to coach ratio is too big break the kids up into smaller more managable groups