When I was in 6th grade (circa 1990) I read a book in my English class... a fantasy/sci-fi book about 2 kids who somehow end up in this government/world where everyone lives on floors. Each floor is like a caste--sort of a physical manifestation of the levels of professions/education, etc. that you find in A Brave New World. In fact this book seems kind of like a kid-version of ABNW. The book is about the kids sneaking floor by floor up through the building. They reach the top to find a floor of people with grass living inside of a dome where they do have the sun and life is good. I don't remember how the book ends... that is the last I remember toward the end of the book.

I would really like to find this book and read it as an adult. Please help!!