Well it comes down to knowing the kids and their individual " foibles " as it were. She will always aske them to hang on til the end of the lesson and most of them do.
I can offer a serious reply. Mrs V teaches Year One at her school and unless it is a genuine " emergency " none of them are allowed to leave for the toilet during lesson time. Reason being that if one can get out of class others will try it on too.
Agree, odd first post.