When it comes to identifying students who need extra help, there are a few different systems schools use to decide what support a child might need and when special education should be considered. Three of the most common models are RTI, MTSS, and the Discrepancy Model.
Understanding the difference between RTI, MTSS, and the Discrepancy Model helps IEP teams make informed decisions, follow Child Find responsibilities, and collect the right data. Whether you’re a new teacher or a veteran IEP team member, knowing how each of these models works will help you better advocate for your students and guide them towards the supports and services they need.
What Is RTI?
RTI stands for Response to Intervention. It’s a method schools use to provide early help, or interventions, to students who are struggling with academics. RTI is typically focused on reading, writing, and math. The goal is to catch students early, before they fall too far behind, and give them targeted instruction.
RTI is built on three tiers.
In Tier 1, all students get high-quality classroom instruction.
In Tier 2, students who aren’t making expected progress get small group interventions.
In Tier 3, students receive even more intensive and individualized support.
A key part of RTI is progress monitoring. Teachers collect data regularly to see if the interventions are working. If a student doesn’t respond to interventions after a reasonable period of time, they may be referred for a special education evaluation.
What Is MTSS?
MTSS stands for Multi-Tiered System of Supports. It includes everything in RTI, but it’s more comprehensive. MTSS looks at both academic and behavioral needs, not just academics.
MTSS also has three tiers, and they work in the same way as RTI. But in MTSS, a student might get support in behavior, mental health, or social-emotional skills, alongside academic help.
For example, a student might receive Tier 2 support for math and Tier 3 support for emotional regulation. MTSS teams often include behavior specialists, counselors, and administrators. It’s a whole-child approach, and data is gathered across areas of need.
What Is the Discrepancy Model?
The Discrepancy Model is an older method of identifying students for special education. It looks for a large gap, or discrepancy, between a child’s IQ and their academic achievement.
If a child has average or above-average intelligence, but is performing significantly below grade level in reading, math, or writing, the team might suspect a learning disability.
This model relies heavily on standardized testing and often doesn’t offer early intervention. A student typically must “fail enough” before the discrepancy becomes noticeable… and that can delay support. Many states have moved away from this model in favor of RTI or MTSS, but it’s still used in some places.
What’s the Difference Between RTI, MTSS, and the Discrepancy Model?
All three models are used to identify and support students who are struggling. However, the key differences come down to focus, timing, and process.
All three models are used to identify and support students who are struggling. However, the key differences come down to focus, timing, and process.
- RTI and MTSS can both be used as part of the special education evaluation process under IDEA, and they align closely with Child Find obligations. The Discrepancy Model is more traditional and may not offer intervention prior to testing.
- RTI and MTSS are proactive. They offer help early and collect ongoing data through classroom-based interventions.
- The Discrepancy Model is more reactive. It waits until there’s a clear gap in ability and performance before taking action.
- MTSS is broader than RTI. It includes behavior and emotional support, while RTI focuses mainly on academics.
How Do These Models Connect to Child Find?
Child Find is a part of IDEA. It requires schools to find and evaluate any child who may have a disability and need special education services.
RTI and MTSS play a key role in Child Find because they help identify students who aren’t making progress—even when they get extra help. If a student doesn’t respond to Tier 3 support in RTI or MTSS, the IEP team may start a full evaluation.
With the Discrepancy Model, Child Find kicks in when a concern is raised, often by a teacher or parent. But the delay in support can make early identification harder.
What Happens if a Student Doesn’t Make Progress?
To support a student in RTI or MTSS, teachers need to collect frequent, consistent, and specific data over time. This can include:
- Classroom work samples
- Weekly progress monitoring results
- Behavior charts or logs
- Notes from small group interventions
- Observations and checklists
This data should show what interventions were used, how often, and whether the student made progress.
In the Discrepancy Model, the main data sources are IQ tests and academic achievement assessments, often completed by the school psychologist during a formal evaluation.
If a student isn’t improving after receiving interventions in RTI or MTSS, the team can refer the student for a special education evaluation. Parents can also make this referral at any time.
The data collected during the intervention process becomes part of the evaluation record and helps the team determine if the child has a disability and qualifies for an IEP.
Even if the Discrepancy Model is being used, any teacher or parent can request a special education evaluation if there’s a concern about learning or development.
When to Refer for Special Education
If a student is not making adequate progress despite receiving high-quality, research-based interventions at Tier 3 with fidelity and documentation, then it may be time to initiate a special education evaluation. Most schools require at least 6 to 8 weeks of data from Tier 2 and another 6 to 8 weeks of Tier 3 intervention before considering a referral, but this can vary by district.
- PRO TIP: Parents can also request a referral at any time, and the RTI/MTSS process should not (and cannot) be used to delay or deny that request. A student does also not need to go through RTI/MTSS to be referred by a teacher for an evaluation.
Understanding the difference between RTI, MTSS, and the Discrepancy Model empowers teachers to better support their students and meet legal requirements like Child Find. While the Discrepancy Model has its place, modern systems like RTI and MTSS are designed to help students sooner and more holistically.
No matter which model your school uses, data is your best friend. Keep clear records, track interventions, and collaborate with your IEP team early and often. When we respond quickly and purposefully, we can prevent small learning struggles from becoming big barriers and ensure every student has the support they need to succeed.
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