Translation of Schmutzfleck

It actually happened to my cousin's youngest kid. He was repeatedly warned not to smoke in the courtyard of the school. At the end he found himself expelled from the school. It could have been an interesting experience for him though.
You have to be careful when you go on summer vacation. There are many dangers but the most dangerous one is the sun itself, because if you're not careful it may harm you. People underestimate the rays.
I live right next to Montpellier, in a small town near the coast, in France. I have no children and I'm learning Spanish because I like foreign languages. I learn vocabulary and grammar. Vocabulix helps me a lot.