Designing effective math SDI: Practical strategies that work

What counts as SDI in math? Moving beyond accommodations

Special educators and administrators across the country are asking the same urgent question: What truly makes math instruction “specially designed”? A recent session we hosted with CASE tackled this question head-on, offering practical clarity on Specially Designed Instruction (SDI) in math and how it differs from simple accommodation or general differentiation.

The math performance gap: Why this matters now

Our session opened with a look at math proficiency in the United States. According to 2024 NAEP data:

• Only 39% of 4th graders are proficient in math
• That number drops to 28% for 8th graders
• And falls further to just 22% of 12th graders

This pattern of early gains followed by later collapse signals that foundational gaps aren’t being fully addressed—and without strong, targeted intervention, skill deficits compound over time. For students with disabilities, the stakes are even higher.

So, what is SDI?

Under IDEA (Sec. 300.39(b)(3)), Specially Designed Instruction is defined as adapting the content, methodology, or delivery of instruction to address a child’s unique disability-related needs and ensure access to the general curriculum.

But SDI is frequently confused with accommodations. The session drew a clear distinction:

In short, accommodations level the playing field, and SDI builds the skills students need to play the game.

The three pillars of SDI in math

Effective SDI adapts instruction across three interconnected dimensions:

1. Content — The What — SDI adapts the curriculum, tools, and manipulatives students need to make progress. This means prioritizing standards for maximum impact, focusing on foundational math skills, and ensuring alignment to grade-level expectations while building access.

2. Methodology — The How — This is where instructional design gets truly specialized. Evidence-based methodologies highlighted in the session include:
   • Concrete–Representational–Abstract (CRA) instruction
   • Explicit modeling of problem-solving strategies
   • Visual models and manipulatives
   • Chunking multistep tasks
   • Vocabulary instruction and guided math discourse
   • Repeated practice with immediate corrective feedback
   • Number sense interventions

3. Delivery of Instruction — By Whom and Where — SDI requires intentional decisions about grouping and setting, shifting fluidly between whole-group, small-group, and one-to-one instruction based on student data. Collaboration between general education teachers, special educators, and math coaches is essential for effective delivery.

What SDI looks like in the classroom

Our session offered a practical observational checklist to help educators and administrators recognize quality SDI in action.

You should see:

• Teachers modeling and thinking aloud
• Small group and one-on-one instruction
• Scaffolding and visual supports
• Frequent student responses
• Structured instructional routines
• Ongoing progress monitoring

You should not see:

• Students sitting passively
• “Help” without instructional purpose
• Independent work replacing direct instruction
• A one-size-fits-all lesson

SDI is a system, not a program

One of the most important takeaways was this: SDI is a system, not a single program or strategy. Effective implementation requires infrastructure, including:

• Shared instructional expectations across teams
• Ongoing professional development and coaching
• Protected intervention time
• Progress monitoring systems
• Collaboration between general and special education
• Accountability at the systems level

Key takeaways

1. SDI is instruction, not just support — it requires intentional, individualized design.
2. High-quality SDI is explicit, systematic, and data-informed.
3. Effective SDI should be observable — if you can’t see it, it may not be happening.
4. Strong implementation requires systems-level leadership.
5. Instructional quality drives student outcomes.

Ready to elevate your math instruction?

Our mission is to empower educators and support students with learning challenges through evidence-back instructional programs. Our multisensory approach, grounded in the science of math, provides special educators with the tools, routines, and training needed to deliver SDI with confidence and fidelity.

Whether you work in a self-contained classroom, a resource setting, or an inclusion model, understanding and implementing true SDI in math is one of the most impactful steps you can take for your students.