Dealing with students at seminars?

This is just a stupid problem to have for starters. are they running a martial arts school or a daycare? Sounds to me like someone passed the buck and left you in charge to do there job! I have taken kids to compete out of state but ALWAYS made one of there parents go! As an instructor it is my job to teach NOT to play baby sitter, but make NO mistake if i told one of them not to do something they knew better. Sounds like there is NO respect in this case so it sounds like thy kid does what she wants and knows she can get away with it. so the problem starts elsewhere to begin with. In ANY school that i belonged too you would learn real fast if you had a respect issue.