I have a policy that states that I will support any child willing and ready to potty train. It is at my descretion when they go into underwear at daycare. They are to wear pull ups until they are initiating the use of the toilet (asking, not being told) and are dry for several days.
I explain to parents that I do not put a child on the toilet every 20 min in hopes that something falls out of them. I offer consistent opportunities for them to use the bathroom, but I'm in no way in a position to force a child to use the toilet.
I keep consistent with the parents plan. I do not offer anything more then a sticker when they do good. (and some hugs and high fives! )
Kids train differently in a daycare environment. Parents need to understand that.