Many parents have good intentions when coaching their children, but end up in arguing matches during tournaments.  If you are one of those parents, then I would recommend taking statistics and reading the statistics to your child instead of giving them your input on how they are not meeting your expectations.  There are many ways to keep statistics, I’m just going to mention 1 basic way - keeping tract of your child’s mistakes.  Talley up the following mistakes during the game:
 
Forehand Loop against Topspin  
 
Backhand Loop against Topspin
 
Forehand Loop against Backspin   II
 
Backhand Loop against Backspin   IIIII
 
Forehand Block
 
Backhand Block  I
 
Forehand Push I
 
Backhand Push
 
Forehand Smash
 
Backhand Smash  II
 
As you can see, there were some major problems – especially with the backhand loop and backhand smash.  After you show the child the statistics, ask the child their opinion on how to fix the problem.  When you look together with them at the hard facts, it is much easier to work at fixing the problem together.