to say actually, no, your DS has not been well behaved?

[grumblinalong]

I have DS1's friend here (as a favour to his mum, past experience has taught me not to volunteer to offer to have him for tea) and his behaviour is a nightmare. In the past hour he has continually slammed the glass living room door, taunted younger ds2 relentlessly, keeps calling the 9 month old baby ugly, trashed ds1's room and shouted rude words in our street. DS1 is desperately trying to get him to stop bouncing on the sofas and watch a dvd. DS looks really worried

I keep telling him off and it is literally like I don't exist, he looks straight through me. His lovely mum will undoubtedly ask how he has been. AIBU to say actually his behaviour has left alot to be desired?

I've got a nearly 9 year old boy. If it was mine I'd definitely want to be told. If the poor mum doesn't know, then how the hell is she going to pull him up on his behaviour?!
He's just going to get away with it if you don't tell her.

I'd want to know.

Children's behaviour often improves quite dramatically when they realise the adults are talking to each other.

Not only that, but she might be in denial, reassuring herself that if her son's behaviour was that bad then someone would tell her...

Def tell her, when she asks tell her he has been a bit difficult today and ask her how is the best way to deal with him if you want to have him over again (which you may not and I can quite understand this ). I have a friend who's ds is a bit of a monster, friend never leaves him at play dates but stay for coffee, he is a similar age. It can be very stressful even with her there, but as we both want him to learn what is socially acceptable behaviour we do persist.