Do you mean me Pogs.
I do intend to chat to my sister and to pass on all the useful info (DGN is obviously her DGD!)
Like you, I had no intention of criticising teachers, but I do query the decision, where made, to deny pupils reasonable access to toilets which I consider to be a basic human right.
If bullying or inappropriate behaviour is such an 'issue' in a school that it is felt necessary to close toilets then I think the school has very serious problems.
Some years ago, with another teacher, I conducted a survey on bullying at a large upper school where I was working. Several sites were identified as being 'hotspots', I don't remember toilets being the most popular, these included corridors outside classrooms, pathways sheltered by hedges, queues in the dining room, P.E. changing rooms etc.
The school then seriuosly re-examined its Policy on Bullying.