The study was conducted in 18 classrooms from two school districts and one regional Head Start agency in two ethnically diverse cities in south central Texas. In one school district, the study took place in six classrooms in a half-day public preschool center. In the other school district, the study was conducted in nine full-day Head Start classrooms located in five different schools. In the regional Head Start agency, the study took place in three full-day Head Start classrooms located in two different schools. Parents did not have a choice of half-day or full-day setting, but were offered the program available in their district.
Schools with a high percentage of children from low socioeconomic backgrounds were selected for the study. The 18 study teachers were randomly assigned to either the Project WORLD intervention condition (11 teachers) or the business-as-usual read-aloud comparison condition (7 teachers). There were 148 children with parental consent who met the eligibility criteria of having well-below-average vocabulary knowledge (indicated by scoring below the 30th percentile on the PPVT-III) and demonstrating English proficiency (as reported by their teacher); of these children, 81 were in intervention classrooms and 67 were in comparison classrooms. The analytic sample consisted of 125 children, with 69 in intervention classrooms and 56 in comparison classrooms. Children ranged in age from 4.0–5.3 years, with a mean age of 4.5 years. The sample of children was 53% female and 47% male, and all of them received free or reduced-price lunch. The racial/ethnic composition was 50% African American, 28% Latino, 14% Caucasian, and 8% Asian American.
The Project WORLD intervention was implemented for 20 minutes daily for 12 weeks. Teachers
conducted the shared book reading sessions with groups of nine or ten children, while the
remaining children were engaged in other activities supervised by the classroom paraprofessional.
The lessons were organized around two science themes, Nature and Living Things, with
each theme being taught for 6 weeks. Each week, the teaching unit focused on one themerelated
topic, with two books per topic, one storybook and one informational book. Children were exposed to one book on the first 2 days and the second book on the next 2 days. The fifth day was a review day. Children received instruction on 68 target words taken from the 24 books in order to develop their background knowledge about the specific topics. During and after book reading, the teachers explained and reviewed target vocabulary, asked questions, and led discussions to engage children in the learning process.
Teachers in the comparison classrooms used their usual style when reading with the whole class, using books they selected from their classrooms or school library. Only three of their selections were the same books used in the intervention classrooms.
Outcomes included two measures in the comprehension domain: the PPVT-III, in which the
children hear a word and select the correct answer from four pictures; and the EOWPVT, in
which respondents are asked to name the objects or the actions illustrated in pictures. For a
more detailed description of these outcome measures, see Appendix B.
Support for implementation
Before the intervention, teachers in the intervention group received a half-day professional
development session, in which the developers introduced Project WORLD and provided
teachers with instructional materials. During the intervention, the teachers also met with
the authors three times to report progress and discuss the obstacles they met with during