What is Common Core? A 2026 plain-English explainer

5 minute readPublished May 15, 2026

Common Core State Standards (CCSS) is the K-12 educational standards framework used by 41 US states for English Language Arts and Mathematics. It launched in 2010 and is the baseline most US K-12 lesson plans cite. Here's what it actually covers, who isn't using it, and how the 2026 landscape looks for teachers planning lessons against it.

Quick facts

Adopted voluntarily by 41 US states + DC + 4 territories.
Covers ELA and Mathematics only. Science uses NGSS where adopted; Social Studies uses C3 Framework + state-specific overrides.
Each standard has a unique code (e.g. CCSS.ELA-Literacy.RL.4.1) for citation in lesson plans.
Nine US states use their own state-developed frameworks instead: Texas (TEKS), Virginia (SOL), Florida (B.E.S.T.), Nebraska (LEARNS), Alaska, South Carolina, Indiana, Oklahoma, Puerto Rico.
Federal mandate: none. Adoption is state-by-state.

What lesson plans cite

A Common Core lesson plan typically cites:

The standard code. CCSS.ELA-Literacy.RL.4.1 (Reading Literature, Grade 4, Standard 1) or CCSS.Math.Content.5.NBT.A.1 (Number and Operations in Base Ten, Grade 5, Cluster A, Standard 1).
The "I Can" statement. A student-facing translation of the standard, e.g. "I can ask and answer questions to demonstrate understanding of a text."
The relevant Mathematical Practice or ELA Capacity. The 8 Standards for Mathematical Practice and the 7 College and Career Readiness Anchor Standards for ELA describe the practices students engage in across content.

For non-Common Core states

If you teach in Texas, Virginia, Florida, Nebraska, Alaska, South Carolina, Indiana, or Oklahoma, your standards framework is state-developed. The structure is similar (strands, grade-level expectations, performance descriptors) but the codes and content emphases differ. AI lesson tools should switch to your state's framework when you set the state in your teacher profile.

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Common questions

What is Common Core?

Common Core State Standards (CCSS) is a set of K-12 educational standards in English Language Arts and Mathematics, adopted voluntarily by 41 US states plus the District of Columbia and four territories. It was launched in 2010 and is maintained by the Council of Chief State School Officers and the National Governors Association. Each standard has a unique code (e.g. CCSS.ELA-Literacy.RL.4.1) that allows alignment to be cited at the lesson level.

Which states don't use Common Core?

Nine states do not currently use Common Core: Texas (uses TEKS), Virginia (Standards of Learning, SOL), Florida (B.E.S.T. Standards), Nebraska (LEARNS), Alaska (state-specific ELA + Math standards), South Carolina (College- and Career-Ready Standards), Indiana (Indiana Academic Standards), Oklahoma (Oklahoma Academic Standards), and Puerto Rico. Each has its own state-developed framework with different content emphases and code structures.

Does Common Core cover Science and Social Studies?

No. Common Core only covers English Language Arts and Mathematics. Science is typically aligned to the Next Generation Science Standards (NGSS), adopted by 20+ states. Social Studies most often follows the C3 Framework (College, Career, and Civic Life), with state-specific additions (New York K-12 Social Studies Framework, California H-SS, etc.).

How is Common Core different from the previous standards?

Common Core was designed to provide consistency across states (which historically had wildly different K-12 standards), to focus on fewer, deeper concepts per grade rather than broad content surveys, and to emphasise the practices students engage in (mathematical practices, ELA capacities) alongside the content. Critics argued the rollout was rushed and the assessment alignment was contentious; nine states rejected or replaced Common Core for those reasons.

Is Common Core still mandatory in 2026?

Common Core itself was never federally mandatory; states adopted voluntarily. In 2026 it remains the operative framework in 41 states + DC + 4 territories. The non-Common Core states use their own state standards. There is no national federal curriculum in the US, the framework you use depends on the state in which you teach.