I don't know if it is like this with all agencies, but when I provided childcare through an agency, the rule with potty breaks was that I had to have direct supervision with every child under the age of 6 yrs old. According to my home visitor I had to either A) take all the children into the bathroom with me so I could still see them or B) line them up against a wall in the hallway just outside the bathroom door and keep the door open.

Now that I am not with an agency I either make sure a family member is able to watch over the children or they are all sitting in their chairs at the table before snack/lunch is served.