Research

Eight studies reviewed by the WWC investigated the effects of Ladders to Literacy on preschool children. One study (Russell, 2005) is a randomized controlled trial that meets WWC evidence standards. One study (PCER Consortium, 2008) is a randomized controlled trial that meets WWC evidence standards with reservations. The remaining six studies do not meet either WWC evidence standards or eligibility screens.

Meets evidence standards

Russell (2005) conducted a randomized controlled trial of 5-year-old children from 12 Head Start classrooms in southern New Hampshire. The 12 classrooms were recruited for the pilot year of the national evaluation conducted by the PCER Consortium (2008) study described below. Because of delays in study implementation, Russell (2005) used a posttest-only design to investigate effects on oral language skills during the 2002–03 school year (one year before the PCER Consortium, 2008, study). Thirty-four children participated in the study; 18 were in the treatment classrooms that received Creative Curriculum^® supplemented with Ladders to Literacy, and 16 were in the comparison classrooms that received Creative Curriculum^® only. At baseline, the children in the study averaged 4.7 years of age, and none of the children were identified as having a disability.

Meets evidence standards with reservations

A study by the PCER Consortium (2008) assessed the effectiveness of Ladders to Literacy as part of the Preschool Curriculum Evaluation Research (PCER) effort.⁵ The PCER Consortium (2008) used a randomized controlled trial design in which 14 Head Start preschool classrooms from southern New Hampshire were randomly assigned to implement Ladders to Literacy as a supplement to the Creative Curriculum^® or to a control group that implemented the Creative Curriculum^® without the Ladders to Literacy supplement. Eleven of the 14 classrooms were randomly assigned the previous year for the pilot, described above (Russell, 2005); three other classrooms were added to the sample. Pretest and posttest data, collected in the fall and spring of the 2003–04 school year, were obtained for 105 children (54 Ladders to Literacy and 51 control). Baseline equivalence on pretests was established for the treatment and control children. The study investigated effects on oral language, print knowledge, phonological processing, and math. Outcomes were assessed at two time points: end of preschool and end of kindergarten. At baseline, children in the study averaged 4.6 years of age, and 25% were identified as having a disability. Although the WWC used only the results at the end of the preschool year to determine the intervention rating, information on the kindergarten findings can be found in Appendices A4.1–A4.4.

Extent of evidence

The WWC categorizes the extent of evidence in each domain as small or medium to large (see the WWC Procedures and Standards Handbook, Appendix G). The extent of evidence takes into account the number of studies and the total sample size across the studies that meet WWC evidence standards with or without reservations.⁶

The WWC considers the extent of evidence for Ladders to Literacy to be medium to large for oral language and small for print knowledge, phonological processing, and math for preschool children. No studies that meet WWC evidence standards with or without reservations examined the effectiveness of Ladders to Literacy in the early reading/writing or cognition domains for preschool children.