By the time my son was in elementary school, it had become, "Don't get involved, get a teacher or call the police."
I think when it comes to non-violent bullying, that people should encourage and empower the bullied to stick up for themselves... and should it become violent, then intercede as necessary.
The day before our debate he and his friends were at a karoke night and his friend tried to intervene when a stranger was bullying another stranger [2] in the sense that "you just don't do that". His friend got stabbed and my partner rode up to Syracuse in the ambulance with him to support him and couldn't come.
I wound up giving both sides of the presentation which fortunately was easy because I had his slides and we'd done enough prep. But yeah, this points out that intervening is a dangerous thing.
When I was in college we had a student, Chris Cater, who was waging a war against gays and had polarized the community around him and created a number of circles of support, for instance some people who were involved in violent attacks, the baptist student union who "loved the sinner but hate the sin", pot smokers who liked that he was criminally minded and was the best dealer because he'd take risks others wouldn't, etc. When he and a friend of mine came by the college radio station and were preparing to prick a can of shaving cream and throw it into a meeting of "gays and friends" I told my friend "Dom, that's dumb, that's really dumb." I didn't see it so much as "taking a stand" but just my spontaneous reaction.
It was the beginning of a whole lot of trouble because Cater and his gang would ambush me at my dorm (stopped the time I ducked into the dorm of the captain of the Rugby team) and when I was out walking. It put a lot of pressure on me because I wasn't really that gay positive at the time and was a stress on my relationships with Christian, pot-smoking, and other friends who found something positive in Cater's charsima and I felt even I was in one of his outermost circles of support and felt the accompanying moral injury because I just didn't want to be involved or seek connections with other victims.
I'm still angry at the school administration because they were slow to intervene and I blame them for the suicide of two students who I think wasn't so much motivated by the attacks but by the failure of institutions to respond -- they don't tell you your life is worthless, they show you.
So yeah, taking a stand can really turn your life upside down.
[1] I tend to become what a group is lacking. Put me in a left-wing group and I am the rightmost, put me in a right-wing group and I am the leftmost. Not so much like I'm a centrist but I think if a class in the Engineering school doesn't have a right-wing engineer in it or somebody like a character in a Heinlein novel something is wrong.
[2] ... I think a continuation of a wider conflict, possibly gang-related
Yes, there are risks in interceding, these risks don't magically go away when someone is in an authoritative position, especially over adults. Police regularly risk their lives expressly to intercede and I fully believe that more citizens should do similar. Why, because police are always minutes away when a violent crime will be over in seconds.
I've literally seen a good citizen with a gun stop a violent crime more times than I've seen Police able to do so. I've also seen similar with unarmed involvements. Yes, there are real world risks, that doesn't mean you stand by and let society decay right in front of you.
There is a risk of citizen action rising and becoming the violent mob as well... this has happened for good and bad outcomes. That doesn't imo mean that you shouldn't try. This is just my own hot take... it doesn't mean I would be comfortable in any given scenario or that I expect everyone else to be... but I would expect more to do so and be rewarded (or otherwise not criminally charged for doing so) than seems to be the case in modern society.
[1] I'm pretty sure he lived but...
Adult cruelty towards children seems to be a thread running through my life.
When I look back on my bullies in school I just see a bunch of messed up kids that were given too much leeway to hurt other kids because adults didn't want to take the time or effort to actually raise and supervise them.
Sone armchair psychology here, but this doesn't seem surprising to me:
One thing a bully needs is to feel strong and secure in their peer group: They feel they can get away with bullying the victim - or even gaining validation - because they believe the majority of the other students are "on their side" and the victim is socially isolated.
If a number of students stand up and call out the bully on their own, they signal to the bully that this is not the case - and that the bully might risk social isolation if they continue.
But if everyone just got an official lesson before to stand up to bullies, this signal falls flat - because it's obvious the students are just "acting on orders" of the school authorities and this is not their real opinion. So the bully might believe they're still "really" siding with them, no matter what they say openly.
For my part, it looked the teachers and administrators offloading the work to students. "Only you can prevent bullying" looks like "I, as a teacher, am not going to bother doing it".
This made me reflect on my own school experience and I've come to believe that some schools and some teachers tolerated bullying because the bullies were doing discipline for the teachers. Maybe not excellent discipline, but it was easy. I also believe some teachers allowed bullying to punish kids they didn't like for whatever reason, nonconformists, smartasses, or minority group. Bullies gave PE teachers plausible deniability.