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Effectiveness
Findings
The WWC review of interventions for Early Childhood Education addresses student outcomes in six domains: oral language, print knowledge, phonological processing, early reading/writing, cognition, and math. The studies included in this report cover four domains: oral language, print knowledge, phonological processing, and math. The findings below present the authors’ estimates and WWC-calculated estimates of the size and statistical significance of the effects of Ladders to Literacy on preschool children.7
Oral language. Russell (2005) analyzed the effectiveness of Ladders to Literacy on oral language using two measures: mean length of utterance (MLU) and type token ratio (TTR). The author did not find statistically significant effects of Ladders to Literacy on either measure, and the effects were not large enough to be considered substantively important according to WWC criteria (that is, an effect size of at least 0.25). According to WWC criteria, this study shows indeterminate effects on oral language.
The PCER Consortium (2008) analyzed the effectiveness of Ladders to Literacy on oral language using the Peabody Picture Vocabulary Test–Third Edition (PPVT-III) and the Test of Oral Language Development–Primary III (TOLD-P:3) Grammatic Understanding subtest. The authors show that differences between the Ladders to Literacy group and the control group are not statistically significant on the TOLD-P:3 Grammatic Understanding subtest and are not large enough to be considered substantively important according to WWC criteria. However, there was a substantively important (but not statistically significant) negative effect of –0.38 on the PPVT-III. According to WWC criteria, this study shows potentially negative effects on oral language.
Print knowledge. The PCER Consortium (2008) analyzed the effectiveness of Ladders to Literacy on print knowledge using the Test of Early Reading Ability–III (TERA-3), the Woodcock-Johnson III (WJ-III) Letter-Word Identification subtest, and the WJ-III Spelling subtest. The authors report that differences between the Ladders to Literacy group and the control group are not statistically significant on any of these measures, although, according to WWC criteria, there is a substantively important negative effect of –0.30 on the TERA-3 and a substantively important positive effect of +0.30 on the WJ-III Spelling subtest. According to WWC criteria, this study shows indeterminate effects on print knowledge.
Phonological processing. The PCER Consortium (2008) analyzed the effectiveness of Ladders to Literacy on phonological processing using the Preschool Comprehensive Test of Phonological and Print Processing (Pre-CTOPPP) Elision subtest. The authors report that the difference between the Ladders to Literacy group and the control group is not statistically significant and, according to WWC criteria, is not large enough to be substantively important. According to WWC criteria, this study shows indeterminate effects on phonological processing.
Math. The PCER Consortium (2008) analyzed the effectiveness of Ladders to Literacy on math using the WJ-III Applied Problems subtest, the Child Math Assessment–Abbreviated (CMA-A), and the Building Blocks Shape Composition task. The authors report that differences between the Ladders to Literacy group and the control group are not statistically significant and, according to WWC criteria, are not large enough to be considered substantively important. According to WWC criteria, this study shows indeterminate effects on math.
Rating of effectiveness
The WWC rates the effects of an intervention in a given outcome domain as positive, potentially positive, mixed, no discernible effects, potentially negative, or negative. The rating of effectiveness takes into account four factors: the quality of the research design, the statistical significance of the findings, the size of the difference between participants in the intervention and the comparison conditions, and the consistency in findings across studies (see the WWC Procedures and Standards Handbook, Appendix E).
7 The level of statistical significance was reported by the study authors or, when necessary, calculated by the WWC to correct for clustering within classrooms or schools and for multiple comparisons. For the formulas the WWC used to calculate the statistical significance, see WWC Procedures and Standards Handbook, Appendix C for clustering and WWC Procedures and Standards Handbook, Appendix D for multiple comparisons. In the case of Russell (2005), a correction for clustering was needed, so the significance levels may differ from those reported in the original study. In the case of PCER Consortium (2008), no corrections for clustering or multiple comparisons were needed.