With these positive findings as a backdrop, this report describes the High 5s program in detail, noting what was needed to implement the program with fidelity to the model. The program set out to achieve a number of goals -- it was designed to build on the content of the Building Blocks curriculum; to deliver hands-on, engaging instruction in a game-like format; and to provide opportunities for both differentiated instruction and for children to delve deeply into mathematical concepts by explaining their mathematical thinking to others. Because the High 5s program was new and developed specifically for this project, and because it aimed to achieve an ambitious set of logistical and educational objectives, it was not clear at the outset whether High 5s could be implemented successfully. (author abstract)