Ages 4 through 56...
I start 4-year olds in "My First Piano Adventures," a pre-school method with lots of graphics and games (Levels A, B & C).
For 5s, I use the Primer from the Piano Adventures series, which has 5 levels. This is a comprehensive core of 4 books: Lesson, Performance, Technique & Artistry, and Theory.
Piano Adventures for the Older Beginner is geared for young teens, and P.A. for the Beginning Adult suits all other ages.