Being a pushy mum works..or does it?

Created a bit of a fuss today at swimming. I asked the instructor why, if DD3 wasn't allowed to move up a class until she was 4, the instructor of the new class had invited two children who weren't even 3 to move up. Not that I was actually fussed especially since DD3 will swim better where she is, but it's the principle. So then I get a phone call from the new instructor saying they'd like to move DD3 up into her class. AARRGGHH. I've taken the place, but what happens if the instructor is horrid to us because I've caused a fuss, and potentially got her into trouble with her boss? As DH said, at least there'll be witnesses if she tries to drown us.
Off to practise "paddle, paddle, breathe, paddle, paddle, breathe" in the bath.