I know exactly how you feel.
Had payments coming in in drips and drabs for 3 days. 1 family paid on time this month.
I've messaged / spoken to all the parents today and got:
oh, I forgot, which I replied with, strange how you don't forget to drop the kids off. Perhaps I should forget to collect from school until you've paid.
A, oh it's nearly Christmas and things are tight this month. Yes it will even tighter when you can't go to work because you have no care for your kids
A couple of half arsed apologies and a well I will get round to paying you, I'm very busy you know.
My end of year newsletter is not going to make for happy reading for some parents.
Oh, and Mr, oh I forgot also didn't bring a coat for his kid when it's 1 degree centigrade here this morning.