Can’t confirm for everyone, but can confirm that 7th grade is when my school district explored ancient history.

I still remember being told the story of the origin of Phoenician purple (pigment/dye.) Something about a dog biting a snail on a beach and its mouth turning purple/blue. I think it stuck in my memory because my first thought was that the snail poisoned the dog, and I was shocked at how casually the teacher told such a sad story. But the teacher continued on to say it was just a pigment covering his face, and I was relieved.