Principle: Focus On What You CAN Do For The Parent/Child, Not What You Can't Do
The More Negative You Are, The More Negative The Parent Will Be
Apart from it not being helpful if you spend your time telling a parent why you can't do what they are asking, it sets up a tone of argument, where you and the parent end up on opposite sides. That's why it's so important to look for things you CAN do.
When faced with parental demands, it's easy to get caught in the trap of telling the parent that you can't do what he or she is asking, and in many cases, you simply CAN'T. The problem is that if your focus is on what you cannot do, you portray yourself as difficult, and not taking the parent's concern seriously.
It's a question of tone and approach, though. Don't focus ONLY one what you cannot do, but look for things that you CAN do. Often there will be small things you can do to help the parent with his or her concern, even when you cannot do what's demanded.
Rather than talk only about the negatives, work to find something, even a small thing, you can do.
To make this work, you need to look beneath the parent's demands, to find out what the real problem is. Then you need to think about things to offer up, in lieu of what the parent wants.
Sometimes, you may find, once you understand where the parent is coming from that you can actually address his or her concern in a better way, one that's more beneficial for the student, and in a way that the parent prefers, if only you LOOK, and seek to understand.