How sad. In a school restroom?
Teachers need to be more in tune with what is going on; certainly it's easy enough to see if a child is being bullied. Looking the other way or talking amongst themselves when they should be watching over their classrooms, locker rooms, lunch rooms, playgrounds, etc. is perhaps happening more often than not.
I've experienced and seen several incidents where the teacher(s) were not paying attention to the students around them.
I used to volunteer for a couple of years and at the time, there was a teacher, one assistant and a volunteer for most classes and class sizes were not that large.