Local newsstory last month.
My boss's daughter attends the school in question, and apparently the facts in the mother's statement are generally correct, except that the boys weren't planning on videotaping his "death" just his "lesson".
This case is almost too extreme to add much to the discussion, in my opinion, but in this case the school officials failed to act and clearly should have.
More generally, kids should be protected against any physical abuse by other students. Schools should be physically safe, or as safe as adults can make them. Teasing is different, although there are kinds of teasing that would persuade me to pull my kid out of school and arrange for alternative education. And any situation that involves MULTIPLE students ganging up on one person should be treated as an emergency by all concerned. Mob activity is too unpredictable and escalates too quickly.
That's the part for the school administration.
Speaking as a possible future parent, kids can and should be expected to treat each other like human beings at all times. My parents always required that of me and my brother both at home and at school. There was no "letting kids be kids and sort it out". There was only "this is what reasonable people do and we are raising you to be reasonable people".
The one time my brother thought he'd try picking on a kid in his class and my parents learned about it, my mother sent him over to the other boy's house and told his mother that my brother would be doing Bobby's chores that week. If any child of mine shows even the remotest evidence of being a bully he's going to learn quickly that it is NOT in his own best interest.