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Six studies reviewed by the WWC investigated the effects of Doors to Discovery™. One study (PCER Consortium, 2008) is a randomized controlled trial that meets WWC evidence standards. One study (Christie, Roskos, Vukelich, & Han, 2003) is a randomized controlled trial that meets WWC evidence standards with reservations. The remaining four studies do not meet either WWC evidence standards or eligibility screens.
One study reviewed by the WWC (PCER Consortium, 2008) assessed the effectiveness of Doors to Discovery™ as part of the Preschool Curriculum Evaluation Research (PCER) effort.6 The PCER Consortium (2008) used a randomized controlled trial design in which 29 full day Head Start and public prekindergarten preschool classrooms in Texas were randomly assigned either to implement Doors to Discovery™ or to a control group.7 Data were collected on 183 children (94 Doors to Discovery™ and 89 control). Pretest data were collected in the fall, and posttest data were collected in the spring, of the preschool year. The study investigated effects on oral language, print knowledge, phonological processing, and math. The control condition varied across sites and included teacher-developed, nonspecific curricula.
One study (Christie et al., 2003) was a randomized controlled trial with severe subcluster attrition and baseline equivalence of the analytic sample. In this study, four Head Start classrooms in a large metropolitan area in the southwest United States were randomly assigned8 to implement either Doors to Discovery™ or the control group, which used materials based on Creative Curriculum®.9 Data were collected on 37 children (21 Doors to Discovery™ and 16 control group). Pretest data were collected during November and December of the preschool year; the Doors to Discovery™ curriculum was implemented from January through early April, and posttest data were collected in late April and May. The study investigated effects on oral language and print knowledge.
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.10
The WWC considers the extent of evidence for Doors to Discovery™ to be medium to large for oral language and print knowledge and small for phonological processing and math. No studies that meet WWC evidence standards with or without reservations examined the effectiveness of Doors to Discovery™ in the early reading and writing or cognition domains.
6 The PCER Consortium (2008) evaluated a total of 14 preschool curricula, including Doors to Discovery™, in comparison to respective control conditions.
7 The study indicated, and the authors’ confirmed, that the unit of assignment was the classroom; however, all classrooms within a school were assigned to the same treatment condition.
8 A fifth classroom participated in the study and implemented the Doors to Discovery™ curriculum. Since this classroom was not randomly assigned, it was omitted from the WWC review.
9 According to Christie et al. (2003), the comparison group was “loosely based” on Creative Curriculum®, a curriculum designed to foster children’s social-emotional, physical, cognitive, and language development, relying heavily on the use of play centers (Han et al. 2005).
10 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. Information about how the extent of evidence rating was determined for Doors to Discovery™ is in Appendix A6.
|Institute of Education Sciences
