I have never had to "prove" that I graduated from high school. But for Beauty School you need to show your high school diploma. Something to do with the state licensing board. You can show your college diploma, but that's not the one they care about. Problem was that my high school diploma does not say the work "high school" on it any where. I'm probably the first person from Horace Mann to go to beauty school, ever. I had to explain "well, it's a snooty private school in New York City and they assume everyone just knows." So then we move on to the college diploma. Problem with that one was that it's all in Latin.
I only got a perplexed look from the Director. Luckily, I was able to produce a college transcript that noted the awarded degree and the fact that I graduated from high school -- all in English with an official stamp. (Transcript was originally obtained for my Mexican working Visa back in 1992 when I worked in the Mexico City office for Grey.)