I teach students in grades 3 through 5 who have been identified as gifted in Math. Although I teach 3 grades, their abilities stretch over many grade levels more than that. (I have students who can already do square roots in 4th grade!)
Our Math book often does not have the breadth or depth needed to help these students achieve their potential learning in Math. I rely on sites like Teachers Pay Teachers to find supplemental materials to engage my students.