I would say a living environment, over a school environment. Sure, everyone can relate to a school environment, but the thing about school is that nobody wants to be there. Firstly, our relationship with the people around you are based off of necessity, out of boredom. While it's relate-able, nobody enjoys it. Secondly, the environment has some sense of falseness about it. It's not a real-life environment. The environment exists for your main characters, but your readers know that realistically, in a few years, those characters won't be in that environment anymore. That environment won't exist and your characters will no longer have the same roles and relationships. If done right, this element can make a good "where are they now" story, but otherwise it's a closed-world story.
A town or city is an open world. Characters can appear out of no where for no reason, there are thousands of different sub-environments, living situations, character types, and tons of different reasons for the characters to be brought together. Not to mention the setting they're in is constantly changing -A school setting is subject to repetition. New elements are less predictable in an open-world setting, and characters are allowed a broader range of motives. In a school setting, the common motive of your characters, of course, is to attend school (and graduate, or whatever). In a town setting, the common motive of your characters is simply to live. At that point, it's a matter of opinion, but in my opinion, a story about surviving in the real world makes for a more meaningful message.
I also think one of the more concrete points to consider is that in a school setting, you have this sort of.. safety net, one that your readers are aware of. You have a staff team specifically trained to ensure the well-being of students. You have a structured, professional environment. Town settings aren't like that, even if their leaders think they are. In a town or city setting, unless the population is extremely small, that safety net just isn't there. Your reader has a stronger sense of the reality of danger the characters may face. There is no trained staff to make sure they eat lunch on time, or give them life advice, or trap them in a secure environment for eight hours a day.
