“Midnight Teacher: Lilly Ann Granderson and Her Secret School” by Janet Halfmann (Lee & Low, $18.95) is an exceptional children’s biography of the life and influence of an unsung hero in African-American and educational history.

Born into slavery in Petersburg, Virginia around 1821, Lilly Ann Eliza Cox was 4 when her mother died.

She was sold to a family in Kentucky. Growing up, she worked in her master’s house; the family children, when the adults weren’t looking, played school with her.

They even give her a blue-back old speller to keep and use. Lilly Ann was eager to learn, but enslaved people in Kentucky were significantly discouraged from being…