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Research
Six studies reviewed by the WWC investigated the effects of Ladders to Literacy. Three studies (O'Connor, 1999, Study A: Intensive Professional Development; O'Connor, 1999, Study B: Traditional Professional Development; and O'Connor et al., 1996) were quasi-experimental designs that met WWC evidence standards with reservations. One study (Fuchs et al., 2001) was a randomized controlled trial with randomization problems that met the WWC standards with reservations. 4 The remaining two studies did not meet WWC evidence screens.
Met evidence standards with reservations
O'Connor (1999, Study A: Intensive Professional Development) examined outcomes of Kindergarten students in a large urban school district. Students in the intervention and comparison groups received the same district-sponsored pre-reading curriculum. Students in the intervention group also did Ladders to Literacy activities. Students in Kindergarten were identified, pretested, matched, and divided into two groups. The WWC review of this study focused on the comparison of 64 typical learners in the intervention group with 41 students in the comparison group. 5
O'Connor (1999, Study B: Traditional Professional Development) examined outcomes of Kindergarten students in a large Midwestern rural school district. Seventeen teachers were assigned to Ladders to Literacy or the comparison condition. Students in the intervention and comparison groups received the same district-sponsored pre-reading curriculum, but students in the intervention group also used Ladders to Literacy activities. In the analysis of the full sample,6 192 students from nine classrooms were in the intervention group and 126 students from eight classrooms were in the comparison group. In this larger replication of Study A, teachers received less intensive professional training.
O'Connor et al. (1996) examined effects of Ladders to Literacy on Kindergarten students in a large urban school district who were instructed by five teachers. 7 Two transition teachers were randomly assigned to intervention or comparison conditions. The three regular classroom teachers were not randomly assigned to the treatment or comparison condition. Students were matched by type of classroom (general or repeating kindergarteners). The WWC focused on the portion of the sample that included 42 students from three classrooms in the intervention group and 24 students from two classrooms in the comparison group.
Fuchs et al. (2001) examined effects of Ladders to Literacy on Kindergarten students in an urban school district located in the Midwest. All students received their regular reading curriculum and the intervention group also received the Ladders to Literacy curriculum. Teachers were stratified by demographic and background features, and then randomly assigned to conditions. After teacher-level assignment, students of different ability levels were selected to be part of the study. The WWC focused on the portion of the study that included 11 teachers with 136 students in the intervention group and 11 teachers with 135 students in the comparison group. 8
Extent of evidence
The WWC categorizes the extent of evidence in each domain as small or medium to large (see the What Works Clearinghouse Extent of Evidence Categorization Scheme). The extent of evidence takes into account the number of studies and the total sample size across the studies that met WWC evidence standards with or without reservations. 9
The WWC considers the extent of evidence for Ladders to Literacy to be medium to large for alphabetics and comprehension and small for fluency. No studies that met WWC evidence standards with or without reservations addressed general reading achievement.
5 The intervention and comparison groups were divided by ability level (at-risk learners and typical learners). The at-risk subgroup was also examined in the study but the groups were not equivalent at pretest according to WWC analysis and therefore did not meet standards.
6 The sample included both typical learners and students at risk of developing reading problems.
7 Two of the five participating teachers taught students who were repeating Kindergarten in "transition" classes and three were in general classrooms. Additionally, two self-contained classes of Kindergarteners with mild disabilities also participated in the study. Because appropriate controls did not exist for children in the self-contained classes, these classes were not in included in the review.
8 The study also included an analysis of the effects of Ladders to Literacy combined with Peer Assisted Learning (PALS). Although this comparison met evidence standards with reservations, it was not considered in the intervention rating because it went beyond the standard delivery of the program. However, results are reported in Appendices A4.1–A4.3.
9 The Extent of Evidence Categorization was developed to tell readers how much evidence was used to determine the intervention rating, focusing on the number and size of studies. Additional factors associated with a related concept, external validity, such as the students' demographics and the types of settings in which studies took place, are not taken into account for the categorization.
