A great many preschools require toilet independence before a two-year-old can start. It is usually presented as being about the child being ready. It is mostly about the adults.
What the requirement actually measures
Children arrive at two with wildly different levels of independence, and very little of the variation is about capability or effort. A rule that gates entry on toileting mostly measures how much time a family has had, and how cooperative a particular child’s body has been. Neither predicts anything useful about how they will do in a classroom.
What it costs a family
It converts a developmental milestone into a deadline, usually right when a parent is returning to work. Rushing toileting to meet a school’s admission date is a reliable way to make it take longer.
How we handle it instead
Toileting is treated like everything else in a Montessori room: at the child’s pace, consistently, with the environment set up so the child can manage as much of it as they are able. Independence is the curriculum, not the entry requirement.
It is worth asking every school you tour, because the answers differ sharply and the policy is rarely on the website.