My Dream of Living in a School

Back in 6th grade I remember reading a ton of books about kids living in the wilderness by themselves. Hatchet, that book about wolves, and so on. There was one we read that I've been thinking about for about the past 10 years but have not been able to remember the name of. It was about these kids who end up living in a school after a mysterious plague sweeps the world killing everyone over the age of 12. I don't know why, but I have always wanted to take over a school building and live in it.  I think I dreamed of that even before reading the book (which I suddenly was able to remember the name of thanks to a particularly fruitful Google search) The Girl Who Owned a City by O.T. Nelson. So anyway, I re-read it a couple weeks ago, along with My Side of the Mountain and then tried to convince everyone I know to read those as well as The Silver Crown by Robert C. O'Brien. All books about kids making it on their own in the wilderness (The Silver Crown has some crystal caves and weird sci-fi stuff going on as well). Why? Because spring is almost here and this year I'm planting a garden and I'm going to be just like these kids making it on their own in the woods, except this will all take place in my backyard in the middle of a city.
Side note: there is a girl who currently lives in a school, in fact 3 school buildings, in rural Kansas. It's called the Harveyville Project and they have sheep and goats there and space to make art. AND, it's in the middle of wide-open kite-flying country. Living in a school in the middle of a huge, blue-skied expanse of land? Sigh.