Q: At what age does a toddler have the hand strength and manual dexterity to wipe his own bottom? His pre-school expects my 3-year-old to wipe his own bottom and he can't really get up "in there" to get it all.
A: Ah, yes, the very common problem of "complete potty independence" required by many preschools. You're right -- many, if not most, preschoolers don't have the dexterity (or desire) to really give themselves a complete wipe. And many parents silently (and with great embarrassment) accept the fact of their preschoolers coming home with "skid marks" on their underwear, since they NEED their child to be able to stay in school -- for work reasons, or otherwise. Shame, constipation, and "poop withholding" are the common outcomes of these preschool rules.
I'm strongly against these stringent requirements. I know that licensing issues are often a problem for schools, but GOOD programs will do their best to work with their toddlers and preschoolers to help them along at this stage. Experienced teachers and administrators have seen this all before, and will have good, workable solutions to help your child. But if you don't get the support your child needs at school, I'd suggest you look elsewhere for a program that understands and supports the developmental progress of young children.