Results of the Three Studies
Vaughn, O'Connor and Tilly all provide intriguing results regarding the implementation of RTI. Essentially, the researchers presented two types of outcomes to evaluate the RTI models. The first set of outcomes they report offered contrasts of student performance on early literacy measures across Tiers. A second set of outcomes focused on the movement of students through the Tiers and into special education. These results are summarized in Table 1.
Table 1. Results: Contrasts of Student Performance
| Vaughn | O'Connor | Tilly |
| GAINS | GAINS | GAINS |
| Early Exit Tier 2
60+ words No Exit 20+ words |
Average students gained .5 SD words | K: 15 seg. (W-S) 1: 30 words 2 30+ words 3: 30+ words |
| COMPARISONS | COMPARISONS | COMPARISONS |
| T1 vs. Control
Significant T1 & T2 vs. Control Significant |
T1 vs. Control
E.S.: .19-.52
Mean E.S. = .34 T2 vs. Control E.S.: .40-.67 Mean E. S. = .55 T2 & T3 vs. Control E. S. < .55 |
Yr 1 vs. Yr 2 (Kind.)
E.S. = .71 Yr 1 vs. Yr 2 (1st) E.S. = ..26 Yr 1 vs. Yr 3 (Kind.) E.S. = 1.08 Yr 1 vs. Yr 3 (1st) E.S. = .39 |
Contrasts of Student Performance.
The Vaughn and O'Connor studies are experimental comparisons of control groups with Tier I, Tier II, and Tier III interventions. Both studies include control groups, random assignment of students, and measures of student growth on letter naming, phonemic awareness, word identification, fluency and comprehension. Vaughn determined that Tier I students made more progress than control group students not receiving Tier I support. Students needing both Tier I and Tier II interventions also made significantly more progress than an equivalent control group. O'Connor provided effect sizes for comparisons. In her study students in Tier I outscored students in control groups across all measures with effect sizes ranging from .19 to .52 with an average of .34. Comparisons of Tier II students with controls resulted in effect sizes ranging from .40 to .67 with an average of .55. O'Connor reports even greater effect sizes for the contrast of Tier II and III students with controls.
Tilly also studied the early literacy growth of all students served in Tiers I, II, and III. For all schools participating in the project he reports raw scores associated with the 20th-50th-80th percentile at each school for the beginning, middle, and end of year. In order to quantify and summarize the extent to which schools improved, Tilly examined the amount schools changed from Year 1 of participation in the HELP project to Year 2 or Year 3 of implementation. Effect sizes were based upon this change and reported for dependent measures of phonemic segmentation and oral reading fluency. For the phonemic awareness task the effect size was .71 for Year 1 to Year 2 change at 85 schools and 1.08 for Year 1 to Year 3 change at 36 schools. On the oral reading fluency task the effect sizes were .26 for Year 1 to Year 2 growth at 86 schools and .39 for Year 1 to Year 3 improvement at 32 schools.
Movement of students through tiers and special education.
Another approach to evaluating the impact of the multi-tier RTI model is to examine the placement outcomes for students participating in the studies. All three researchers did a follow-up on eventual placement of students. These data are shown in Table 2.
Table 2. Results: Movement of Students Through Tiers
| Vaughn | O'Connor | Tilly |
| 45 Tier II Students Early Exit: 10 Mid Exit: 14 Late Exit: 10 No Exit: 11 24.4% to Tier III |
Control:
15% to Spec. Ed. Tier I: 12% to Spec. Ed. Tier II & III 8% to Spec. Ed. |
Decreases in Spec. Ed. Placement Rate
At 36 Schools Decrease in Placements: Kindergarten 55% 1st Grade 32% 2nd Grade 21% 3rd Grade 19% |
Vaughn studied 45 second grade students who qualified for Tier II intervention. She reported the number of students needing further intervention or returned to the general education setting at 10 week intervals. Near the beginning of the study 10 students had progressed enough to warrant "early exit" (10 weeks), 14 students qualified for "mid-term exit" (20 weeks), 10 students improved enough for "late exit" (30 weeks), and 11 students (24.4% of the sample) did not meet the criteria for success in Tier II. Vaughn theorized most students identified at risk need at a minimum 20 weeks of intervention before concluding they are non-responders.
For O'Connor, about half the students in Tier II did not make good reading progress. In Tier III she notes almost 40% of the students maintained average performance without needing additional assistance. She went on to examine student outcome by tabulating the number of students needing special education after interventions in the multi-tiered process. For her control group, 15% of the students were ultimately determined eligible for special education. For students who were engaged only in Tier I interventions the percentage of students going on to special education was 12%. For those students that participated in the total three tier model (Tiers I, II, and III) the rate of students placed in special education was 8%. Tilly also examined placement rate in special education. He reviewed the special education placement files at schools with the longest implementation of the HELP project (n=36). He compared placements rates from the three year period prior to implementation of HELP to the four year period after implementation. Placements in special education decreased at all grade levels, including: 39% in kindergarten, 32% in first grade, 21% in second grade, and 19% in third grade.
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