I don't know if this counts, but I do remember one teacher in the second grade told me, the way I write the number 4 would be wrong. I wrote it with the triangle, a closed tip, just as you see in most fonts. My teacher was unhappy about it and told me the tip of the 4 should be open. She forced me to write a whole sheet of paper at home with 4's just the way she writes it. I cried, it was unfair, and asked for support from my mother, but she shrugged and said: "If you teacher wants this, do it."
I am still mad about this nonsense. Today I use to write my 4 just with the tip closed, stupid teacher.