What kind of literary technique is "living behind closed doors,"?

0) "you're not here to read books, you're here to learn! " the childwrangler's voice screeched as we kept our picks moving rhythmically against the school walls. we had all heard about a time, back in the dark ages, when children read books at school. they say school was even a building above ground. but that was obviously dangerous. how could society thrive if the children sat around reading all day? when would they have time to learn about veins of coal, support structures, processing fuel, and all that stuff? school was important. which two central ideas in this story are most closely related?