If the behaviour is in any way dangerous to myself or any of my children, then I immediately step in and intervene, no questions asked. If the ehaviour isn't dangerous but is merely distressing for my child, I will usually look around to see if the other parent notices first, and also allow my child a chance to deal with the situation themselves - however I am ready to step in if it escalates or if my child has done all they can and the bad behaviour is persisting (will be different for different aged children, younger ones will need you to step in sooner). I don't step in for every little thing, and think it is good for kids to learn to handle things on their own - but I do definitely keep an eye on the situation and stay ready to step in if needed.

But I generally have no problem stepping in and telling any child "no", particularly if their parents fail to care (there is a big difference between not noticing that your child is hurting another, and noticing but failing to get involved). Generally most parents around seem to be OK with this. I am certainly happy for strangers to tell my children "no" if they are behaving badly. However occaisionally you will get some parent who thinks that their child is always above reproach. Tough luck to them, I feel sorry for those children.

When my DD was about 18 months old, she was playing in one of those car rides that you put the money in (we never do, it was just stationary). An older child (would have been about 3yrs) came up and tried to move her over to get in himself. The mother was watching and couldn't have cared less - just kept catching on her phone. I went over and asked him to be careful as she is only little. When I turned to look at the mum again, he 'pushed' her out of the car onto the floor. The mother was atching him, still didn't care. I was livid. I picked up my crying DD, Told the little boy " NO, that was very mean. You DON'T push little kids." (In my stern teacher voice) The mother suddenly got interested - offended at how dare I talk to 'her' little angel like that! She doesn't believe in disciplining children! That poor little boy is going to get into so much trouble in his life, and he is going to be clueless as to why, because his mum is failing to teach him basic respect for others.