Light Yagami/Harry Potter
Light was right. It took three more months for Dudley to be dropped from the gifted program and go to a normal pre-KG. Dudley was happy, Vernon and Petunia were not.
Best of all? Light kept the books. They were boring but Light needed to know what was expected of gifted children in the 80s. He only knew about the 90s. There were way too many differences in expectations between the decades.
As a bonus, Petunia's face took on a most unpleasant expression whenever she saw Light flip through Dudley's old books. She looked like she wanted to snatch them out of his hands and burn them in a bon fire. She didn't. By now, it was clear that snatching anything from Light's fingers would result in a tantrum. Dudley's tantrum, that is. God forbid their darling Diddykins ever felt upset about something avoidable.