No, it is an optional add-on for those who would like full-color and reusable boards for some of the board games in the book. It sure is fun, though!
About 10% of the games in the book require a game board. (Most of the card games, handwriting and spelling games, active games, and creative practice ideas do not.)
Of the games that use a Game Board, a few can be played only with a board from the Expansion Pack, while others use a black-and-white reproducible master from the back of the book or let you choose a full-color Expansion Pack board or a black-and-white master. This means that you'll be able to play over 95% of the games in this book even if you don't have an Expansion Pack.
However, the boards in the Expansion Pack are a lot of fun, so we recommend adding them if you can! Four of them are bigger than the templates (11x17 instead of 8.5x11), and the full-color, lively illustrations are delightful. They also have a glossy texture that allows you to add words or phonograms to practice with a dry-erase marker.
Quantity note: Most of the board games in the Game Book are designed for 1-4 players. If you are teaching in a classroom setting you may want to order multiple Expansion Packs so all of your students can play.