Key Curriculum Press is publisher of great math curriculum like the Key to series and Miquon. If you are looking for a way to introduce geometry before highschool the Key to Geometry can teach children as young as 10 years old how to bisect angles, reproduce segments, do sophisticated constructions and introduce them to over 130 geometric terms. The Key to ... books are not only easy to learn from, but also to follow along with if you, the teacher, are a little foggy on these topics!
Key Curriculum Press also publishes the Miquon Math series. Miquon Math introduces all four arithmetic operations and fractions in the first year! By the third year children are graphing algebraic equations!