Two Markets, One Classroom: How Core and Supplemental Materials Shape Student Learning

The Center for Education Market Dynamics • March 26, 2025

Understanding the Role of Core and Supplemental Curriculum

Teachers use both core and supplemental materials to support student learning, but these resources follow very different paths from selection to classroom use. While core curricula are selected through formal district-level processes, supplemental materials are often chosen by individual schools or even individual teachers. This disconnect can make it difficult to build a cohesive instructional system that supports student success.

For state leaders and education organizations that provide targeted assistance, understanding how these two markets function is essential to helping districts navigate procurement and align resources effectively.

Two Markets, One Classroom

The supplemental curriculum market is vast. Data from CEMD shows that across 1,700 districts, over 350 different supplemental math products are in use across K–8. In contrast, selection of high-quality core curriculum typically involves choosing from fewer than 20 programs.

The overwhelming number of supplemental choices makes it challenging for educators and leaders to identify the best resources. Without careful selection, these materials can distract from, rather than reinforce, high-quality core instruction.

Adding to the challenge, districts rarely select core and supplemental materials from the same provider. Large, established publishers dominate the core curriculum market, while smaller companies fill the supplemental space with specialized products. As a result, instructional materials often lack alignment, making it harder for districts to design coherent lesson plans from the start of the school year.

Different Rules, Different Priorities

Core and supplemental materials serve distinct purposes and operate under different market forces:

• Core curriculum must meet rigorous state standards and provide a comprehensive learning experience. These materials are designed to align with grade-level expectations and district priorities, providing a coherent scope and sequence that addresses the needs of all learners.
• Supplemental materials have more flexibility. Unlike core curriculum, supplemental products aren’t expected to remain as stable over time. Since these products require less investment to modify, publishers can update them more frequently. While this adaptability can be beneficial, giving educators access to new and innovative features, it also means that products change more often, sometimes creating misalignment with core instruction.

Because of these differences, districts must actively work to ensure that supplemental materials support—not disrupt—their core instructional goals.

How Districts Choose Core vs. Supplemental Materials

Districts follow different processes when selecting core and supplemental materials:

• Core curriculum selection is a structured, lengthy process where districts extensively evaluate a limited number of products against district and state criteria. Contracts typically last 5–8 years.
• Supplemental materials are often chosen in a more ad hoc manner. Districts may purchase multiple resources to fill gaps, and schools or teachers may adopt additional site-based tools independently. Contracts are often shorter (one-year with renewal options), and many “freemium” products are designed to gain teacher buy-in with basic features, encouraging individual classroom use in hopes of “converting” that use into larger district-wide purchases.

While this flexibility allows districts to respond to emerging needs, it can also lead to a patchwork of materials that don’t align or reinforce each other—or the core curriculum—making it harder to create a focused learning experience for students.

Bridging the Gap

Core and supplemental materials both play critical and distinct roles in student learning. However, the differences in how these materials are developed, marketed, and selected means that district leaders and educators bear the burden of piecing them together to create a connected learning experience.

To create a more cohesive instructional system, districts need clear strategies for selecting and integrating core and supplemental materials. This means not only ensuring content alignment but also considering how materials support instructional goals, professional development, and long-term planning. By prioritizing coherence, districts can build stronger instructional systems and ensure that materials work together to support student success.

Key Questions

District and school leaders looking to select new materials or plan for next year can ask questions to engage and support increased coherence:

What criteria guide your district’s selection of supplemental materials to prevent a fragmented instructional system?

• How does your district evaluate the quality, impact, and alignment of supplemental materials before purchasing?
• What questions should you plan to ask vendors about how core and supplemental materials work together to support Tier 1 or Tier 2 instruction?

How do you support educators in integrating core and supplemental materials in lesson plans?

• What guidance, training, or support do you provide to ensure teachers select and use supplemental materials that are intentionally designed to complement the core curriculum used in classrooms?

How does your district ensure that supplemental materials support, rather than compete with, core curriculum?

• What processes help maintain instructional coherence across classrooms and grade levels when supplemental materials are selected separately from core curriculum?
• What support is needed to align student outcomes to the intended impact of supplemental materials?