COLUMBUS, Miss. (AP) — For the past three years, Heather Henry has taught seventh grade math at New Hope Middle School. More specifically, she teaches pre-advanced-placement math, attracting the brightest, most ambitious students.

"She's the best of the best," said her principal, Sam Allison. "I don't say that lightly, either. There are some teachers you can shut the door and not worry about. Heather is one of those teachers."

Henry, 40, has taught 14 years, but this year stands apart because — on top of instructing students on the normal curriculum — she has been teaching something not found...