Not on the original question about the teacher, in regards to bathrooms.
A lot of this depends on the administration. Some principals are like psychos about this stuff. We had one reduce the passing time from like 7 minutes to 5 minutes. Some of these kids had a very long haul to get from one class to the next. However, he and an assistant principal "timed their trip", if they could walk from one end to the other in that amount of time, so could the kids according to him. This made no allowance for bathroom or even stopping to tie your shoes.
He also set a limit, 2 free trips per semester. After that a tardy for each trip. After a couple those, you get after school detention. That made it really hard for the kids. Of course it made it hard for the teachers too, you have to STOP what you are doing and log each kid's trip to the bathroom, when they left and when they get back. His line was "you can't learn content in the hallway". Disrupting an entire class is much easier for everybody than just letting somebody go.

He would also collect the logs every month. Whether or not he actually looked at them, well I doubt it. I think it was just a power thing. A lot of teachers, myself included just kinda selectively did it, only log it when if came handy. He never said anything to me about it.
The last year I was there, the administration came up with a better idea... instead of the teachers dropping everything to log this stuff. The kids would log themselves out! They put clipboards with a form on it in every classroom next to the door. This was genius! (
NOT). Well let's see, Batman went to the bathroom today, oh look Justin Beiber signed out. Oh yes, the kids would write other kids names instead of their own. Of course kids would draw "things" on the sheets. It was just a disaster.
Of course you get the kids in there who have a 504 who are allowed unlimited trips... the other kids are saying "Why does such and such get to go so much"? It is just a disaster created by the administration.
Where I am working now (in a sub capacity), the administration is pretty relaxed about this stuff. With block scheduling, many (if not most) of the teachers allow a "break" during class. The kids have about 5 minutes or so to wander around, go to the bathroom, get a drink and come back. The kids look forward to it, and you can use that as a reward. It really cuts down on people wanting to go during instruction because they KNOW they will have a chance at a certain time. Sacrifice 5 minutes of instruction to save a lot of hassle and disruption? Yes, it makes sense to me.
It seems that so many times administrators are doing stupid things just to have a "policy" in place. "IF this, THEN this"... It seems as if they want to remove themselves (and I guess the school entirely) from actually having to think or use any kind of judgment.
OK I am ranting, I will be quiet now.