Unit 2 described how Mathematics: K–8 Learning Progressions develop within and across grade spans.

The categorical areas of the CCSS for Mathematics are:

- Standards: Define what students should understand and be able to do.
- Clusters: Groups of related standards (standards from different clusters may be closely related because mathematics is a connected subject).
- Domains: Larger groups of related standards (standards from different domains may sometimes be closely related).

The six domains for Grades K–5 are:

- Counting and Cardinality (K only)
- Number and Operations Base Ten
- Number and Operations Fractions (Grades 3–5)
- Operations & Algebraic Thinking
- Geometry
- Measurement and Data

The six domains for Grades 6–8 are:

- Ratios & Proportional Relationships (Grades 6–7)
- The Number System
- Expressions & Equations
- Geometry
- Statistics & Probability
- Functions (Grade 8 only)

Learning progressions:

- Are ways of characterizing what happens as students learn mathematics
- Have a web-like structure
- Incorporate several domains

Standards:

- Support and depend on many other standards
- Are part of several different progressions
- Support student learning within and across a grade span

**Instructional Alignment Charts** support teachers as they study standards within and across grade levels and consider implications for instruction and assessment. They contain four sections:

- Standards for Grade/Course
- Changes
- Levels of Instruction
- Implications for Instruction and Assessment

Student engagement is enhanced through the use of 21st Century Skills such as:

- Innovation and Creativity
- Critical Thinking and Problem Solving
- Communication and Collaboration
- Information Literacy and Digital Citizenship