Hello everybody

I have open classes coming up as I'm sure others do this month and I'm generally fine with all classes except for one 5th/6th grade class who can be a real sullen lot when they want to be.
I teach at two schools and the two eldest groups from each school couldn't be more chalk and cheese. At the one school, they love the ideas I have for games and love singing pop songs and oldies and are just generally very receptive to whatever it is I lead the class with.
The other school not so much.
Anyway, they will do a presentation for the open class and I will teach some key words and expressions and suchlike before that. My question is this, does anybody have any warm up exercises they use for the first ten minutes to get the students talking? Any general plan that is tried and tested for open classes?

Thanks