My oldest did not go to a preschool with the potty training policy. I also taught at that preschool and I had to clean up a number of messes. It is just the life of a mom and teacher.
I just read this article on a three year old who was potty trained but the schedule the school set for potty breaks threw this little girl off and she stared having accidents. The school suspended her for a month because she broke their potty training policy. The mom found a school with no potty training policy and she has not had an accident since. This is crazy. I had pressure to train my youngest because she could not go into a church class or preschool class without being trained. Fortunately she was easy but this is crazy. You have to be flexible with kids. Accidents should not be punished. You need grace. If a child was potty trained and all the sudden had accidents you need to find out why not automatically suspend them.