I have experienced this in a few different way in the past school year. One of my students loved to make TikTok videos. She brought her phone into the class room to shoes me one of her videos and I was blown away. It was extremely inappropriate for a 4th grade student (language and gestures). She explains to me that this is normal and showed me more videos. I was mortified!
The other mistake made was allowing students to look at my screen while printing coloring pages for them. The pictures that they want are usually anime and at times inappropriate pictures have come up and I have to quickly exit the tab.