I’ve not been in a school since the 1980’s and I though things had moved along a little bit.
In London at least, you would not have got away with this in the 1980’s (believe me, I was there). In my multi-ethnic borough ‘baa baa black sheep’ was banned at one point! In some ways it was more sensitive than things are now.
My experience was that racist kids got it from their racist parents. Most believed (or were taught) it was harmless, and as superior white Englishmen, we were entitled to belittle every other race! Some became enlightened, some (generally the thick ones it has to be said) grew up into racist adults.