If a parent tells you about how their child was the star pupil of the week in their class, ask them how many children are in their class and say 'Hmmm, 27 kids divided by 34 weeks of term...isn't every kid going to be best pupil of the week eventually?'
Follow this up by proudly patting yourself on the back safe in the knowledge that you've needlessly put a bummer on someone's day.