K-2
3-5
Algebra encompasses the relationships among quantities, the use of symbols, the modeling of phenomena, and the mathematical study of change. The mathematical investigations and conversations of students in the elementary grades frequently include elements of algebraic reasoning. These experiences present rich contexts for advancing mathematical understanding and are an important precursor to the more formalized study of algebra in the middle and secondary grades. For example, when students in grades 3 through 5 investigate properties of whole numbers, they may find that they can multiply 18 by 14 mentally by computing 18 x 10 and adding it to it 18 x4, thus using the distributive property of multiplication over addition in a way that contributes to algebraic understanding.
As with number, these concepts of algebra are linked to all areas of mathematics. Much of algebra builds on students’ extensive experiences with number. Algebra also is closely linked to geometry and to data analysis. The ideas of algebra are a major component of the school mathematics curriculum and help to unify it. (Principles and Standards for School Mathematics: An Overview, NCTM)