I was a teacher and am shocked at this ruling. At the beginning of each academic year, parents in my school had to fill in an admin form, stating any medical conditions of pupils, so we were usually aware of children with medical conditions, who needed to frequent visits to the loo. This info would be updated throughout the year. Supply teachers were advised of this info, which was kept on a database, easily accessed by ALL staff, including pupil support assistants. Any named child was advised to catch the teacher's eye and just slip out without disturbing the lesson. Also, I knew those pupils, who would ask to go out, just to get out of the lesson. If a child who never asked to go out, asked, I knew that there was a problem and would send them immediately. It's all about common sense.