April 2017: Achievement Gaps for Students With Disabilities

Schulte, A. C., Stevens, J. J., Elliott, S. N., Tindal, G., & Nese, J. F. T. (2016). Achievement gaps for students with disabilities: Stable, widening, or narrowing on a state-wide reading comprehension test? Journal of Educational Psychology, 108, 925–942. 

Summary by Dr. Nancy Scammacca


An achievement gap is a persistent pattern of differences in level of academic achievement between groups of students who differ on a demographic characteristic. Previous research has documented achievement gaps based on factors that include socioeconomic status, limited English proficiency, and disability status. These achievement gaps have been observed in students’ level of academic ability at the start of school and in the pace of their gains in academic proficiency over time. Closing or reducing the magnitude of these gaps is among the goals of many education reform initiatives at the state and federal levels. Given that reading comprehension proficiency is critical for learning across the curriculum, addressing achievement gaps in reading is particularly important, especially for students with reading disabilities.

Schulte, Stevens, Elliott, Tindal, and Nese (2016) analyzed longitudinal data from the North Carolina state reading assessment for students in grades 3 through 7 to look for patterns of differences in initial level of reading ability in grade 3 and in rate of growth over time for students with disabilities, academically gifted students, and typically achieving students. They also examined the data for differences based on demographic characteristics such as socioeconomic status, race/ethnicity, gender, and limited English proficiency.

How Growth in Reading Occurs

There are a number of theories regarding the way in which students grow from being nonreaders to being proficient at comprehending text. One theory, known as the simple view of reading, states that reading comprehension is the result of two skills: decoding and language comprehension. Skills such as phonemic awareness, inference-making, vocabulary knowledge, and others provide a foundation for developing word recognition and language comprehension abilities. According to Schulte et al. (2016), students with learning disabilities (LD) most often have difficulty with word recognition and its underlying skills, and students with intellectual disabilities typically struggle with both word recognition and language comprehension. Delays in the acquisition of either or both skills result in delays in developing reading comprehension. Once students with delays develop the needed underlying skills for comprehending text, it is possible that a period of rapid growth in comprehension skills would follow. This period of growth might occur later for students with disabilities than for typical students. Schulte et al. noted that this delayed growth might account for differences in reading comprehension growth rates between typical students and those with disabilities at different points in time.

Three Growth Patterns

Schulte et al. describe three patterns of growth over time that differ in their implications for achievement gaps.

  • Initial differences in ability between groups of students increase over time as students with higher initial ability grow faster than those with lower ability. This pattern is often referred to as the “Matthew effect” or a fan-spread pattern. It would result in widening achievement gaps over time.
  • Initial differences in ability between groups of students decrease over time as students with lower levels of initial ability grow at a faster rate. This pattern is known as the fan-close pattern and would result in narrowing achievement gaps over time.
  • Students of all levels of initial ability grow at a similar pace over time. This pattern is one of stable differences over time where the size of achievement gaps would be maintained.

Pfost, Hattie, Dörfler, and Artelt (2014), in a meta-analysis summarized here, synthesized the results of 78 studies that looked at these reading growth patterns. They found that patterns differed depending on the reading skill examined and the quality of the reading assessment, with evidence for each of the three patterns found for one or more reading skills. However, they excluded studies of students with disabilities from their analysis, so less is known about how these patterns might be present in reading growth data where students with disabilities are compared to general education students and academically gifted students. Additionally, most previous studies have not controlled for the effect of demographic variables, such as socioeconomic status, that may contribute to differences in patterns of growth. Studies that included students with disabilities and controlled for demographic differences have generally not found a fan-spread pattern of increasing achievement gaps over time, but results have been mixed.

Study Purpose and Methodology

Schulte et al. sought to add to the knowledge base on patterns of reading growth over time for students with disabilities, general education students, and academically gifted students. Their purpose was to compare the growth of these groups of students over multiple grades, controlling statistically for demographic differences. They wanted to determine which of the three patterns of growth characterized the growth of students with disabilities compared to general education students and the growth of academically gifted students compared to general education students.

To address their research questions, Schulte et al. analyzed scores on the North Carolina End of Grade Reading Comprehension Tests, the state’s reading assessment, starting with all students who took the test in 2003 when they were in grade 3 and tracking their scores through their grade 7 assessment. The state changed the reading assessment the following year, making it difficult to compare scores across a longer span of time. Assessment results from nearly 100,000 students were included in the analysis. About 13% of the students had disabilities and nearly 6% were academically gifted in reading. Students with reading LD comprised 4.7% of the total sample. To be designated as having LD in North Carolina at the time the data were collected, a student had to have a discrepancy of 15 standard score points or more between their IQ and achievement test scores.

To analyze the data across the 5-year timespan, Schulte et al. used an approach known as hierarchical linear modeling. This approach accounts for the fact that students’ scores over time are correlated. Scores from each year of testing (at level 1 of the model) are nested within students (at level 2 of the model) to reflect the relationship between the same student’s score on the assessment at different points in time. Using hierarchical linear modeling, Schulte et al. analyzed longitudinal growth models to discover and compare the patterns of reading growth over time for students with disabilities, gifted students, and general education students. These models allowed the researchers to determine the effect of demographic variables (gender, race/ethnicity, socioeconomic status, and limited English proficiency) and control for their influence on growth patterns.  

Key Findings

  • At the first assessment (grade 3), students with limited English proficiency and those who were black, Hispanic, American Indian, or of multiracial ethnicity had lower scores than other students. Female students and Asian students had higher initial reading scores. These results were calculated across all students, without regard to disability or gifted status.
  • When disability and gifted status were added to the analysis, students with disabilities had lower initial reading scores than general education students and gifted students had higher scores than general education students (no comparison between students with disabilities and gifted students was made).
  • For all students, the slope for growth over time was curvilinear (meaning that growth did not occur at a consistent rate). All students experienced faster growth up to grade 5, when their growth rate slowed considerably.
  • Differences in patterns of growth over time between students with reading LD and students with other types of disability also were found. Students with reading LD had significantly lower reading scores in grade 3 but experienced more rapid growth through grade 7 than students with other disabilities. Students with reading LD also grew at a faster rate than students with other disabilities and general education students through grade 5, when their growth slowed. By grade 7, their rate of reading growth was below that of general education students.
  • In contrast, academically gifted students had slower rates of growth than general education students through grade 5. But by grade 7, their rate of growth outpaced general education students.
  • The overall pattern for the growth of all three groups of students was one of stable differences over time. The average reading score for each group was different at each time point, with gifted students having the highest average score and students with disabilities having the lowest average score. Within the subgroup of students with disabilities, students with reading LD had average scores that were among the lowest of any disability type at each time point.
  • The achievement gap between students with disabilities and general education students did not decrease meaningfully over time. Students with reading LD made the most progress in narrowing the gap of any disability subgroup. However, the magnitude of the gap left students with reading LD 0.83 standard deviations behind general education students at grade 7.

Implications and Recommendations for Practice

  • The finding that students make larger gains in earlier vs. later grades aligns with the simple view of reading theory. In the earlier grades, students make larger gains in reading comprehension because they experience growth in both components within the simple view of reading (word recognition and language comprehension). Growth slows as students’ word recognition skills plateau and their language development becomes more critical to their ability understand texts in the later grades.
  • One possible explanation for the faster growth seen among students with reading LD is that these students were receiving instruction aimed at developing their word recognition skills. As they achieved greater proficiency and speed in decoding, their comprehension skills would be expected to grow rapidly for a period of time. The slowdown in growth rate seen after grade 5 in students with LD could reflect deficits in skills that undergird language comprehension, such as vocabulary, inferencing, and background knowledge.
  • Based on Schulte et al.’s findings, intervention for students struggling with decoding and other word recognition skills in the early primary grades may help these students catch up before deficits in these skills derail their reading comprehension.
  • Students with LD in grades 3 and above may require reading instruction that focuses on both word recognition skills and building their background knowledge, vocabulary, and other skills required for language comprehension to avoid the deceleration of their reading comprehension growth rate that was seen after grade 5. Given that the achievement gap between students with LD and general education students remained quite large at grade 7, one way to narrow the achievement gap for students with LD may be to provide interventions that help them to remain on the more rapid growth pace they achieved in grades 3 to 5.


Pfost, M., Hattie, J., Dörfler, T., & Artelt, C. (2014). Individual differences in reading development: A review of 25 years of empirical research on Matthew effects in reading. Review of Educational Research84, 203–244.