A Meta-Analysis of Treatment Outcomes (Executive Summary)
Background and Purpose
In the last 20 years, the number of children classified as having learning disabilities has increased substantially, from roughly three-quarters of a million in 1976 to more than 2.6 million in 1997. These children currently make up almost half of schools' special education population, yet it is still unclear which teaching strategies best help these children. Furthermore, a review of past literature reveals few systematic analyses of instructional approaches for students who have learning disabilities. This lack of clear direction creates confusion about how best to educate these students.
Clearly, students with learning disabilities are a heterogeneous group and no general or single intervention can be recommended for these students. However, this report can offer recommendations from its investigation of evidence derived from many different studies on teaching students with learning disabilities. In this meta-analysis we synthesize research on the effects of various forms of instruction intended to improve students' academics (e.g., reading, mathematics), cognition (e.g., problem solving), or behavior (e.g., social skills).
The meta-analysis includes 272 studies which met four criteria. Each study had to:
- Include learning-disabled students of average intelligence who were assigned to an experimental or a control instructional condition.
- Include information on how students with learning disabilities were selected.
- Explain treatment outcomes.
- Have no severe flaws.
We analyzed the effects for a range of studies that included both studies of a single area and studies that examined a mix of subjects across the following: instructional domains (e.g., reading, mathematics); sample characteristics (e.g., age, intelligence); intervention parameters (e.g., number of instructional sessions); and methodologies.
This synthesis examining research conducted over the last 30 years produced several findings related to intervention for students with learning disabilities. Unless otherwise noted, these findings come primarily from the group-design studies.
What forms of instruction were most effective?
The most effective form of teaching children with learning disabilities combined components of direct instruction (teacher-directed lecture, discussion, and learning from books) with components of strategy instruction (teaching ways to learn such as memorization techniques and study skills). The main instructional components of this combined model include:
- sequencing (e.g., breaking down the task, providing step-by-step prompts);
- drill-repetition-practice (e.g., daily testing, repeated practice, sequenced review);
- segmentation (e.g., breaking down skills into parts and then synthesizing the parts into a whole);
- directed questioning and responses (e.g., teacher asks process or content questions of students);
- control of task difficulty;
- use of technology (e.g., computers, presentation media);
- teacher-modeled problem solving;
- small-group instruction; and
- strategy cues (e.g., reminders to use strategies, think-aloud models).
Of these components, the one most linked to effect on student achievement was control of task difficulty (where, for example, the teacher provided necessary assistance or sequenced tasks from easy to difficult.) Another influential component was the use of small interactive groups of five or fewer students. A third strongly influential component was the use of structured questioning and directed responses, involving, for example, interactive questions and answers or the teacher directing students to ask questions and summarize.
Children with learning disabilities perform closer to nondisabled (age-related peers) children when treatment includes strategy instruction. Not surprisingly, nondisabled students generally outperform learning-disabled students. Importantly, however, there was less difference between the performance of the two groups when learning-disabled students were exposed to treatments that included strategy instruction compared to competing treatments like direct instruction.
In the area of reading, both phonics and whole word (whole language) instruction make a significant contribution to student achievement in reading. Neither clearly supersedes the other in terms of transfer measures (reading real words and comprehending text).
Only a few instructional components successfully predict effects on student achievement. Although several instructional components seem to produce effects when studied independently (e.g., segmentation predicts outcomes on phonological measures), the results vary more widely when instruction reflects the variance shared across components. This happens because individual strategies typically do not appear in isolation in a classroom, and often their importance as predictors is enhanced in the context of other components.