We can agree to disagree. Either way, it's not so rare as to be unexpected in an elementary school environment.
A 6 year old can still get worked up and be unable to express her feelings verbally in a meaningful way, which can lead to a tantrum or meltdown especially if there's an underlying medical condition. I know the after school meltdown is a real thing with early elementary age kids. Or a meltdown when they're tired, or had a long day with lots of activity. I don't think a tantrum or two is cause for concern.
From the American Academy of Pediatrics:
https://www.healthychildren.org/Eng...ication-discipline/Pages/Temper-Tantrums.aspx
"
Choose your battles and accommodate when you can. Sometimes you have to give in a little to settle yourself; that’s OK. However, your consistency from day to day is key in reducing the level and frequency of tantrums. So is time. Although most tantrums happen in 1- to 3-year-old children, many children continue to throw tantrums into the school years."
That link also mentions a zero tolerance policy for hitting, kicking, etc.
Whew it's hard being a parent. Once my friends started having kids and I started hanging out with the kids more, I had more sympathy for the times when kids have tantrums and meltdowns. Sometimes you just gonna let it run its course (if there's no danger to the child or anyone of course). I definitely don't judge strangers when I see it in public.
I can't imagine working in a high school when kids get violent. I'd just call security and get out of the way.