The author is a substitute teacher.

Courtesy of Robert Lynch

Teaching is a grubby profession. Any romantic fantasy gets beaten out of you pretty quickly. Kids flip you off in the hallway, and a lesson you spent three hours preparing can go down the toilet in 10 minutes because half the class is checked out and the other half is staring at a phone hidden under their desk.I've taught for over 20 years in universities, high schools, middle schools, and elementary schools. The most common response I hear from teachers to "How's it going?" is a sarcastic "Living the dream."It's a dumb cliché, but it conveys how actual teachers — especially those in working-class public schools — view their jobs.It's been even more difficult for me because I'm now a substitute teacher — even though I have a Ph.D.I wasn't always a substitute teacherI am not the first person to experience social mobility in reverse. But there's a sobering humility to it when it happens to you — to someone who had always assumed they were on the way up.I have a Ph.D. in biological anthropology and trained under Robert Trivers, arguably the greatest evolutionary thinker since Darwin. Before academia, I traded derivatives on Wall Street. After several unsuccessful tenure-track job applications, I taught high school chemistry.