I believe that interacting with a variety of other children at social functions is an important part of childhood development. However, there seem to be a **lot** of children who are... how shall I phrase it? Undisciplined.

Undisciplined behavior in other children can have direct impact on your child, no matter how well behaved. Poor behavior in other children can serve as a bad example, or it can result in upset, or even injury, for your child (think chronic hitters, biters, and bullies).

Even normally well-behaved children can have bad moments, too, especially when in a group environment where situations can escalate much more quickly than normal.

However, disciplining other people's children is a potentially touchy subject, especially given the wide range of opinions of child raising "best practices". I know some schools of thought advocate "never saying no" to a child, and many advocate very different approaches to setting boundaries.

So, how do you handle poor behavior in other people's children? 

How do you respond when the child has a parent present who does not respond in a way that you are comfortable with?

How do you respond when you are the chaperone, and there are no other parents present?