You stop it immediately if not sooner. You sit them down and findout what it is that is on their minds and angering them to the point they are being disrespectful to you.
You do not tolerate it and if you do not stop it you will find yourself with a child that nobody wants to be around because they are obnoxious and not well behaved.
If children who are disrespectful to their parents and get away with it they will be disrespectful to any adult anywhere anytime and this will cause much pain as they grow.
Lady Darko