You're wrong. Those kids will remember for the rest of their lives that a teacher called them monkeys.
I still remember a time in the 9th grade (1985), when I corrected an adult at some event in our high school gym by informing her I was a boy and she responded that if I didn't want to be mistaken for a girl I should get a haircut and lose weight. Every time that memory bubbles to the surface (and it has, often), I feel the shame she wanted me to feel followed by anger that she went out of her way to **** on a 13-year-old kid. Maybe if I'd been able to "cash in" or at least see her suffer consequences for shaming a kid for his appearance, I wouldn't feel the same way all these years later.