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This was only about 5-6 years ago but there was a book I remember reading a lot of in High School.
It was about a girl and her little brother who lived in this sewer city beneath another city, there was a lot of cement.
Their school bought into this government program to feed the kids a weird paste and then they all were playing VR pod "games" with aerial battles.
Turns out the government was trying to build an army, the siblings find out the people living above them are the uber rich, both groups think outside this cylinder is nothing but death and pollution, but after going over the wall in a plane they find lush forests where the uber-uber rich are living.