Reading comprehension--the ability to understand the meaning of text--is a foundational ability that enables children to learn in school and throughout life. Children who struggle with reading comprehension in the third or fourth grade are at high risk for dropping out of school, with detrimental effects on their future employment, income, and participation in the social and political aspects of life. Given the modest and inconsistent effects of existing large-scale early literacy interventions, the Institute of Education Sciences at the U.S. Department of Education commissioned this study to investigate additional types of instructional practices that hold potential promise for promoting young children's language development and comprehension. Using an exploratory design, the study team collected extensive information about instructional practices in prekindergarten through grade 3 within Title I schools and examined the relationships between these practices and student growth in a range of language and comprehension outcomes. Findings from this study are intended to help identify potentially promising practices that ought to be studied further and evaluated on a large scale. As designed, this study makes three key contributions to the existing body of research about the relationships between instructional practices and young children's language and comprehension growth: (1) the exploration of a wide range of instructional practices; (2) the use of student outcome measures that cover a range of language and comprehension skills; and (3) the exploration of the relationship between practices and student growth on a large scale. First, the study explores a wider range of instructional practices than those that formed the basis for recent federal early literacy programs. As discussed earlier, programs such as Reading First and Early Reading First promoted instructional practices focused on the five skill and strategy areas identified by the National Reading Panel, drawing upon substantial research that had found positive effects of these practices in smaller-scale settings. Because these programs, for the most part, did not have their intended effects when widely implemented, this study collected information on an even broader array of practices to search for those practices that might be related to student growth and could therefore be evaluated further. Beyond the practices emphasized by the expert panels, the authors considered practices that encourage students' oral language, expose them to knowledge of the world, stimulate higher-order thinking, help them focus on the meaning of texts, and encourage their engagement in the classroom. Second, the study examines student outcome measures that cover a range of language and comprehension skills. Successful reading comprehension depends on a number of other outcomes that form a foundation for being able to understand text, including a variety of language skills and background knowledge about the social and natural world. For instance, a large synthesis of research found that language measures covering a variety of skills were much more strongly correlated with subsequent reading comprehension than measures focused narrowly on particular skills, such as vocabulary alone (National Early Literacy Panel 2008). However, many previous studies examined the effects of instructional practices on only particular outcomes that were closely aligned with the practices being considered (see Chapter IV for a detailed discussion). For example, although some studies investigated the effects of vocabulary instruction on vocabulary improvement in the early grades (see, for example, Beck and McKeown [2007] and Penno et al. [2002]), almost none determined whether the effects carried over to other aspects of language development and, ultimately, to reading comprehension. There have been exceptions in which a small number of studies (which took place concurrently with the present study) have examined the effects of early-grade language instruction on a range of outcomes and even longer-term comprehension outcomes (see, for example, Lyster et al. [2016] and Dickinson and Porche [2011]), yet most studies have generally examined a smaller set of outcomes. This study contributes to existing research by examining outcome measures that encompass diverse language skills, aspects of background knowledge, and ultimately reading comprehension. Third, the study examines relationships between practices and student growth on a large scale. The findings are based on data collected from 83 Title I schools in 9 states, in which the study team observed instructional practices in over 1,000 classrooms and administered assessments to nearly 5,000 children in the 2011-2012 school year. The size of this exploratory study is important because its findings are intended to suggest the types of early literacy practices that ought to be evaluated on a large scale. Given this study's exploratory design, it cannot provide conclusive information about the effectiveness of instructional practices and is not meant to make recommendations for actual classroom instruction. Instead, the goal is to suggest directions for future research on practices that may promote language development and comprehension. The main body of this report presents, in brief, the study's methods and main findings. Chapter II outlines the design of the study, the types of data collected, and the methods used to collect and analyze the data. Chapter III presents the findings for all students as well as specific groups of students. Chapter IV discusses the study's contributions to prior research and possible avenues for future research. The following are appended: (1) Supplementary Information on the Selection and Characteristics of the Study Sample; (2) Supplementary Information on Study Instruments and Data Collection; (3) Analytic Methods; (4) Additional Results; and (5) Classroom Observation Rubric and Coding Form.