"The Common Core State Standards in mathematics were built on progressions: narrative documents describing the progression of a topic across a number of grade levels, informed both by research on children's cognitive development and by the logical structure of mathematics. These documents were spliced together and then sliced into grade-level standards. From that point on the work focused on refining and revising the grade-level standards."
A student centered discussion about the importance of progressions.
Examples of progressions and making connections.
How students in primary grades develop mathematical skills to count numbers.
The progression of addition and subtraction from grades K-2
The progression of multiplication from grades 2 & 3.
The progression of division from grades 3-5.