I think sometimes the problem is the parents whom don't seem to watch their children. I go along to playgroup with my children to do something with them....not for a break and a coffee and chat whilst I let my child run wild IYKWIM. I am constantly amazed at the amount of parents who don't get involved with their child and what they are doing, you don't need to shadow them but you can come up and see what they are doing and be acitvly involved.

Most of the time if the situation isn't too much of a problem and the other parent has not stepped in I take my child way "come on Charlie, let's play over there" ..... or "that's ok, we will get the puzzles out...do you want to help me?" I try this instead of telling anyone off. I don't see one child taking another child's toy as naughty - sharing is a concept they don't actually fully understand til age 3. So that's a situation I would just take my childs focus away if the other parent is not there to step in. Taking a toy back from a child that doesn't understand is going to cause more drama.

As for things like throwing rocks, or sand etc I tell them gently to please stop in the hope the parent will hear and step in. Again I take my child away if the other child does not stop or gives me attitude. I can only ask them to stop, and explain why it is not my place to disicpline anyone else child and I myself would be very annoyed if someone tried to discipline mine.

It's good to remember we all see it from a different point of view and the most we can do is take care of our own.