I teach 5th graders and found this works for me and my students: On the first day of school, each child receives two laminated bathroom passes. I made these out of construction paper and ran them through the laminating machines. (I actually try to make them during the summer, and then just write their names on them in permanent marker when I get my class list) Mine say: "Mrs. Givens' Gotta-Go-Now! Pass" They also have a cute clip-art of some type on them. I explain to the students that they only get two passes to go to the bathroom for the day, and that they cannot go while I'm teaching in front of the class, so that limits them to when they are doing classwork of some kind and they don't miss an important lecture or set of directions being given for something. Two passes are really enough, I've found, because the kids realize by the first week or so of school, that they can ask the PE coach if they can go or the art or music teacher when they're with them. I can't control that, of course, but the two passes really help in the classroom time. Last year, I had a couple of boys or three or four girls who wanted to go to the bathroom first thing in the morning to talk or whatever, and this really limited that. They really think before they go because they know they only have two passes. Hope it works for you! I realize it might not be a good idea for the tiny ones!