Sounds more like a scenario that your son and his friend were also too "independent" and took off to the bathroom without informing the group leader that they were leaving the group. Does he also believe that the teachers are his employees, therefore can do whatever he wants? I would love to hear the teacher's side of the story.
Yes, I would too.
My mom's friend taught pre-K for 20 years at a private school with very entitled parents who felt the need to be as involved as possible, but who also felt they did not have to follow rules because they paid an exhorbitant tuition.
This is a Toddler-8th grade school where the teachers sit with the students at lunch - there are no aids. Once a year the teachers have an appreciation luncheon, run by parent volunteers. Some parents served the lunch to the teachers, others volunteered to oversee the students' lunches. The Pre-K does not eat in the main dining hall, but in a separate room in the school so it is smaller and not as chaotic. There were three classes of 12 kids each, and a parent for each table, of maybe 4-6 kids. The kids have assigned seating and it was normally a very organized process.
Enter the parents on this particular day. As the class walked to lunch, kids asked if their moms would be there, etc. One little girl asked, and my mom's friend said no, honey, your mom isn't here today as they entered the lunch area. After that chaos erupted, the parents started calling out to their kids to come and sit with their friends. The teachers told them there was assigned seating. They completely ignored it. The parents brought along younger siblings to lunch, despite being asked not to. Therefore there were not enough seats for the students. Kid were dragging chairs, running around, and administrators were pushing along the teachers to their special lunch and telling them not to worry, the parents had control.
Well, 30 minutes later when the teachers returned, they realized a kid was missing. It was the girl who asked if her mom would be there, and I guess she got upset because she wasn't. But no one saw her leave, no one caught that she was missing (she went back to the classroom to play), etc.
Had the assigned seating been honored, a kid would have noticed her missing given how routine oriented 4 and 5 year olds are, there also would have been a missing seat had it not been taken up by a two year old. Had the parents simply allowed the teachers to walk the students in without calling out and disrupting their normal routine, again, this wouldn't have happened. Had the administrators allowed the teachers to settle the kids in and done a headcount instead of "saving face" by saying the parents have this, this would not have happened. There were a million little things that went wrong, which all added up to a big wrong, and it was mainly the parents' faults. Could the teacher have gone back to check and done a head count a few minutes later? Yes, I will say that is possible, but given that this tradition went on for many years without issue, and she was told by her administrator to go enjoy lunch, she didn't do that.
The child in question was fine - as I said she was playing. But that is not acceptable - the panic that ensued until they found her was terrible. And as a result, the teacher in charge was suspended for 4 weeks while the school "investigated what went wrong" to appease the parents of the child. The administrators made her life so miserable, which was so unfair. As a result, policies were changed after this incident. And I can easily see why teachers just want to be left to do their jobs - too many cooks in the kitchen, as they say.