had a mobile phone in their pockets, which at the time had exactly three apps
At the time I was in school (90s to early 00s), cell phones were for making phone calls. There were no "apps." There was no texting, no camera, none of that. Smart phones came out the year I graduated high school. Before that, cell phones were not anywhere near as common as they are today. At a certain point, they were even a status symbol. My elementary school teachers definitely didn't have the money to afford something so fancy in the 90s.
The closest thing I had as a kid was an "electronic organizer" with no phone/internet abilities. That had a calculator and a calendar, but it was more of a novelty and a toy - not something I relied on or would bring to school.