SLD identification: discrepancy vs RTI vs patterns of strengths and weaknesses
By the IEP Atlas editorial teamLast updated
Short answer
Schools identify a specific learning disability with one of three methods: an IQ-achievement discrepancy, a student's response to research-based intervention (RTI), or a pattern of strengths and weaknesses (PSW). Each state chooses which methods its districts may use. States must allow RTI and cannot require a discrepancy. Every method also needs low achievement, exclusionary factors ruled out and an observation.
Federal rules leave the method for identifying a specific learning disability (SLD) to each state, within limits. A state must not require a severe discrepancy between intellectual ability and achievement. It must permit a process based on the student's response to scientific, research-based intervention. It may permit other research-based procedures, which in practice means patterns of strengths and weaknesses.[1] Districts then follow the criteria their state adopts.
All three methods sit on the same foundation. The student must not achieve adequately for age or state standards in at least one of eight areas, despite appropriate instruction. The team must rule out other causes, such as vision or hearing loss, intellectual disability, emotional disturbance, cultural factors, economic disadvantage or limited English.[3] And someone must observe the student in the learning setting.[4] The methods differ only in the second piece of evidence the team uses to confirm the disability.
The deciding question
Ask: is the team judging how the student responds to good teaching over time, or how the student's own test scores compare with each other? Response over time is RTI. Comparing scores within one student is discrepancy or PSW. Discrepancy compares one ability score with one achievement score; PSW looks at a profile of cognitive processes and achievement areas.
Side-by-side table
| IQ-achievement discrepancy | Response to intervention (RTI) | Patterns of strengths and weaknesses (PSW) | |
|---|---|---|---|
| Definition | Achievement is well below what an IQ score predicts | Student does not make sufficient progress with research-based intervention | Strengths and weaknesses in achievement or cognitive processes that fit an SLD profile |
| Basis in law | States may allow it but may not require it[1] | States must permit it[1] | Allowed as an alternative research-based procedure[3] |
| Core data | Cognitive and achievement test scores | Progress monitoring data over weeks or months of intervention | Cognitive processing, achievement scores and their links |
| Who decides | The eligibility group, including parent, teacher and a qualified evaluator[2] | Same group | Same group |
| Strength | Simple to compute; familiar | Rules out lack of instruction; links data to teaching | Explains why the student struggles; useful for planning |
| Common criticism | "Wait to fail"; hard to show in young students | Depends on intervention quality and fidelity | Research on its reliability is mixed; models vary |
| Example finding | Ability score 108, reading 78: a 30-point gap | Grade 2 reader grew 0.4 words per week while peers grew 1.2 | Weak phonological processing linked to weak decoding; average reasoning and math |
| Where documented | Written SLD report[5] | Written SLD report, including strategies used and data collected[5] | Written SLD report[5] |
What each method looks like in a file
Discrepancy. The file holds an intelligence test and an achievement battery. A state using this method sets how big the gap must be, often in standard deviations or a regression formula. Many states have moved away from requiring it because young students rarely show a large gap until they have fallen far behind.
RTI. The file holds universal screening results, a description of each intervention tier, how often and how long it ran, and graphed progress monitoring data. The glossary entry on RTI and the MTSS entry summarize the frameworks. When RTI is used, the written report must list the instructional strategies and the student-centered data, and show parents were told about the data being collected and their right to ask for an evaluation.[5] The guide to using intervention data in an SLD evaluation walks through the analysis.
PSW. The file holds cognitive processing measures, achievement scores and a written explanation of how a specific processing weakness accounts for the specific achievement weakness, while other areas stay intact. Different PSW models use different rules; the state or district usually names one.
Three scenarios
1. A state that requires RTI data. Mateo, grade 1, sits in a district where state rules require RTI data for SLD. After 12 weeks of tier 2 and 8 weeks of tier 3 phonics, his nonsense word fluency has barely moved. Answer: RTI. Why: The state requires it, and his data show low achievement and poor response despite sound instruction.
2. A state that allows PSW, with a student new to the district. Priya, grade 5, transferred in October with no intervention records. Her writing is far below grade level. Testing shows weak processing speed and fine motor skills with strong verbal reasoning and reading comprehension. Answer: PSW, if the state permits it. Why: There is no intervention history to analyze, and waiting months to build one would delay a needed decision. A school cannot use RTI to delay an evaluation a parent requests.[6] The team still needs data showing she had appropriate instruction.
3. A district that still allows discrepancy. Ben, grade 4, has a full scale score of 112 and a reading comprehension score of 79. He had one year of reading support with no progress data kept. Answer: Discrepancy may be permitted, but the case is weak. Why: Without data showing appropriate instruction and repeated assessment, the team cannot rule out lack of instruction, a requirement under every method.[3] The team should start progress monitoring now.
When teams use more than one
Many states let teams combine sources. A team may use RTI data as the main evidence and add a cognitive profile to plan instruction. Or it may use PSW and include whatever intervention data exist. Combining is fine as long as the method named in the report is one the state allows and the report explains how the evidence fits it.
The eight achievement areas are explained in the eight SLD areas. The SLD eligibility report template shows how each method is written up. For the student-level view, see IEPs for specific learning disabilities, and for goals the library page on goals for specific learning disability.
Frequently asked questions
Which SLD identification method is best?
No method is best everywhere, and the choice is not the team's alone. The state decides which methods districts may use. Within those, the best method is the one the student's records can actually support with sound data and that rules out lack of instruction.
Can a school refuse to evaluate until RTI is finished?
No. Federal guidance says a school cannot use RTI to delay or deny an evaluation when a parent requests one. The school must either start the evaluation process or give prior written notice explaining why it refuses.
Is the IQ-achievement discrepancy still used?
Some states still allow it, but federal rules forbid states from requiring it. Many states have moved to RTI, PSW or a combination. Check your state's SLD criteria to see what your district may use.
Use it in IEP Atlas
- RTI in the IEP glossary
- MTSS in the IEP glossary
- IEP goals for specific learning disability
- Specific learning disability in the IEP glossary
Related guides
- The IEP evaluation process: from referral to eligibility
- Using intervention data in an SLD evaluation
- SLD eligibility report template
- IEPs for specific learning disabilities and ADHD: goals, supports, eligibility
- The eight SLD areas and goals for each
- Can a school delay an evaluation for RTI?
Sources
- 34 CFR §300.307: Specific learning disabilities, U.S. Department of Education (IDEA website)
- 34 CFR §300.308: Additional group members, U.S. Department of Education (IDEA website)
- 34 CFR §300.309: Determining the existence of a specific learning disability, U.S. Department of Education (IDEA website)
- 34 CFR §300.310: Observation, U.S. Department of Education (IDEA website)
- 34 CFR §300.311: Specific documentation for the eligibility determination, U.S. Department of Education (IDEA website)
- OSEP Memo 11-07: Response to Intervention (RTI) (January 21, 2011), U.S. Department of Education, Office of Special Education Programs
Written and checked by the IEP Atlas editorial team under our editorial policy. This guide describes general practice and federal rules. It is not legal advice; your state may add requirements, and the IEP team makes the decisions for each student.