You should say that then. "I am concerned but not complaining" I know the child is a little old for this but maybe if you don't see a change in time for your new starters then you could consider just putting the child in a playpen upstairs and out of the way to calm down to prevent things from escalating. The other option is asking her mother to see if she can make some changes to her routine temporarily so she can bring her child after the others are dropped off until they have settled in as she causes a lot of disruption. Ideally you want to have dealt with this prior to them starting but if its not resolved in time then these are some ideas to prevent all out chaos and a negative experience for the other children. Always reassure the parent that you aren't complaining and that you want to work with the parent but that you have to work together by doing the same things in order to reinforce each others actions to the child. Unity and consistency are extremely important. I am very thorough and honest with all families to prevent them from taking things the wrong way and I invite them to talk to me about things versus me just telling them. Obviously there is a way of telling a parent that "this is how it is" but there is a way of making them feel like you are in their corner working with them, not against them or criticizing them, which I know you aren't doing but it is common that parents take it as such.