Luke learned a few things on his desert world.
Tattoine didn't exactly have a schooling system. Instead, he learned a little here and there. Officially, he mostly learned from Aunt Beru. She taught him what was expected, the Empire-based history of the galaxy.
She taught him what life probably was like for his father, how it definitely was for his grandmother. She taught him soft songs. She taught him how to hide his real self under a placating smile. It wasn't a lie, she taught, when it was used for survival. Aunt Beru's family had been on Tattoine a while. Slavery was in her blood like it was in his.
She and Uncle Owen together taught him to read and write. Sometimes Luke's Huttese and Basic would blend together into a grotesque chimera. But people on Tattoine would understand.
Aunt Beru taught Luke how to listen to half-truths. He learned by looking at her eyes that seemed so sad and regretful. The expression on her face whenever she mentioned his family was pained. And for someone who clung so fiercely to the history of Tattoine, she barely mentioned her own family.
Uncle Owen taught Luke to and look at the shift of a posture over what someone was sometimes saying. His sand-aged face seemed almost permanently stuck in a frown of disapproval. It made the other children around Anchorhead squirm. But Luke knew how to look at the softening of his uncle's shoulders, and the grasp of his hands, at the miniscule relaxation of the corners of his mouth.
Luke's uncle taught him some mechanics and welding, skills necessary for survival. The sand would wear away the vaporators in the wind. Parts would be stolen, sometimes just ripped out of place. And you couldn't always buy what you needed. You would have to create some monstrous mishmash of wires and metal and hope that maybe it would work.
Uncle Owen liked mention that one of the things he knew of Luke's father was that he liked mechanics. Luke's grandmother had told Owen stories of Luke's father scavenging from parts. She claimed Anakin had built a droid by the age of nine. Luke was decent at mechanics, especially if it meant he could pour over the blueprint of an old Clone-Era ship. He wasn't a genius though, like his father, and he knew it.
Luke's aunt taught him how to cook. How to use spices to make the meager meals they had seem grander. How to make the most of little.
Later, when the war was mostly over and Luke could cook on his own, he marveled at how many ingredients he could get. He no longer was living on Tattoine or eating rations. He didn't understand most of the fruits and vegetables and even the meat.
Luke learned basic math. On Tattoine, that seemed enough.
Aunt Beru noticed Luke liked math. A lot. There weren't a lot of textbooks to buy him. She managed to get him some on algebra and geometry. She didn't know anything advanced herself, so Luke would spend some of his free time struggling through the pages. The content was especially dry, with little passion in the writing. He did manage to power through them by the time he was 19.
Luke knew a bit about the world, already, when he joined the Alliance. But fighting in a rebellion is different than growing up among Hutts, scavengers, slaves, and farmers. He came off as naïve, despite everything he'd been taught.
When he was 19, Luke realized how little he actually knew.
