Most of the children we have round are well behaved and polite, but occasionally there is one that just isn't.
I usually try to jolly them along and/or ignore it, praying for home time, but I wouldn't put up with the behaviour from my own children, which invariably deteriorates when in the company of these more challenging boys.
I feel I need to put my foot down a bit, but I really don't know what I can/should do when it's not my children.
I had an appalling experience with DS1's last birthday party, where there were 2 boys I hadn't had back before (and won't be again). I was so concerned that it was a party and I didn't want to spoil the fun etc, that I had no control at all. There was answering back, unkindness to DS2 and food throwing I had no clue how to deal with it, but am actually quite strict with my own