I've sometimes not been able to suppress a laugh when telling off my own children, but there's so much more at stake for the head if the kids don't take him seriously, which probably concentrates the mind.
I cringed a bit at the comment made by the girl about immigrants coming over and being given more money by the government than English people. Obviously it was what her parents say, but it shows the sort of attitudes teachers are up against when trying to run a multi cultural school harmoniously.