Why was your friend embarrassed by what the teacher said? I'm very curious. Also, when you describe "dark skin", what exactly is that?

Here in the US, where I now live, "Dark skin" is used with some interpretation, as we have such a mixture of skin tones and races. What might have been called a "Black" person about a decade ago, can be easily confused with an Hispanic, or any mix of races. And don't forget the tanning booths, spray tans, colored and straightened hair, contacts, plastic surgery, etc.!

Although, I doubt back in the 60's those were issues.