That can be the case, but you still need to pay attention to the essay prompts. The guy with the sick girlfriend was writing a requested 250 wd essay for Yale on a topic of his choice, in addition to his PS.
But even if they did say to write about what ever you want, how does being a good econ teacher matter when you're going into law school? If taht's the angle you want to go, I'd just stick with working in construction, and how you were always an academic or something. And give examples of what you learned doing that impacts your daily life or something. But if I was an adcom (which, admittedly, I'm not. You just asked for our opinions) I really don't care all that much how whatever you did made you a better econ teacher, unless I understood how you being a better econ teacher will translate into the legal field.
For this specific school, they've given you an essay prompt, and gave you the bare bones of what they want answered. I suggest you at least try to give them something that flows in that general direction