The present article considers a fundamental question in evaluation research: "By how much do program effects vary across sites?" The article first presents a theoretical model of cross-site impact variation and a related estimation model with a random treatment coefficient and fixed site-specific intercepts. This approach eliminates…

This multiyear scale-up effectiveness study of Open Court Reading (OCR) involved approximately 4,500 students and more than 1,000 teachers per year in Grades K-5 from 49 elementary schools in seven districts across the country. Using a school-level cluster randomized trial design, we assessed the implementation and effectiveness of Open Court…

Attending high-quality early childhood care and education (ECCE) is associated with higher cognitive and social-emotional skills, especially for children growing up in poverty, but access to high-quality ECCE is limited. This study capitalizes on the random assignment design of the Head Start Impact Study to better understand whether the…

Multisite trials, in which individuals are randomly assigned to alternative treatment arms within sites, offer an excellent opportunity to estimate the cross-site average effect of treatment assignment (intent to treat or ITT) "and" the amount by which this impact varies across sites. Although both of these statistics are substantively…

The purpose of this replication study was to examine the impact of the Teacher Study Group (TSG) professional development in vocabulary on first-grade teachers' knowledge of vocabulary instruction and observed teaching practice, and on students' vocabulary knowledge. Sixty-two schools from 16 districts in four states were randomly assigned to…

Experimental evaluations that involve the educational system usually involve a hierarchical structure (students are nested within classrooms that are nested within schools, etc.). Concerns about contamination, where research subjects receive certain features of an intervention intended for subjects in a different experimental group, have often led…

This article describes the effects of an analysis-of-practice professional development (PD) program on elementary school students' (Grades 4-6) science outcomes. The study design was a cluster-randomized trial with an analysis sample of 77 schools, 144 teachers and 2,823 students. Forty-two schools were randomly assigned to treatment, (88.5 hours)…

In this paper, we describe findings from a three-year evaluation of a well-developed mathematics professional development program that is commercially available on a wide scale. The professional development is designed to improve teachers' mathematical knowledge for teaching and to enable them to elicit more student thinking and reasoning during…

This study investigates the effects and feasibility of an intervention for first-grade students at risk for reading difficulties or disabilities (RD). The intervention was provided by general education classroom teachers and consisted of 15 min whole-class comprehension lessons (Tier 1) and 30 min Tier 2 intervention sessions in word reading,…

The present study used a randomized control trial to examine the effects of a widely used multicomponent Tier 2-type intervention, Passport to Literacy, on the reading ability of 221 fourth graders who initially scored at or below the 30th percentile in reading comprehension. Intervention was provided by research staff to groups of 4-7 students…

Given the dearth of high-quality curriculum materials aligned with the new standards (NGSS and CCSS) and low student persistence in STEM fields, we sought to develop and test a STEM curriculum that would improve student knowledge, interest, and emotions. A cluster randomized control trial was conducted to assess the impact of Speedometry, a…

This study examined the efficacy of a core kindergarten mathematics program, Early Learning in Mathematics (ELM), a 120-lesson program with four content strands: (a) number operations, (b) geometry, (c) measurement, and (d) vocabulary. The study utilized a randomized block design, with 129 classrooms randomly assigned within schools to treatment…

The purpose of this study was to evaluate the efficacy of Promoting Acceleration of Comprehension and Content Through Text intervention implemented with 11th-grade students enrolled in U.S. History classes. Using a within-teacher randomized design, the study was conducted in 41 classes (23 treatment classes) with 14 teachers providing the…

This article examines the effects of one year of exposure to "Learning to Read in a Healing Classroom" (LRHC) on the reading and math skills of second- to fourth-grade children in the low-income and conflict-affected Democratic Republic of the Congo. LRHC consists of two primary components: teacher resource materials that infuse…

A multi-cohort cluster randomized trial was conducted to estimate effects of rich vocabulary classroom instruction on vocabulary and reading comprehension. A total of 1,232 fourth- and fifth-grade students from 61 classrooms in 24 schools completed the study. Students received instruction in 140 Tier Two vocabulary words featured in two…