Martine van der Pluijm

20 Chapter 1 This thesis follows the four phases proposed by McKenney & Reeves (2012) and Plomp (2009). During the first phase, we conduct a literature review to improve our understanding of existing programs and their effects on child language development. The second phase consists of a design study applying iterative cycles of testing to improve the prototype and the design principles of the At Home in Language (AHL) program. We use formative evaluations to investigate how the prototype can be customized to the needs of parents and teachers. We apply a case study design characterized by the proximity of researchers to involve stakeholders in the process and become well informed of the specific context and needs (i.e., alpha and beta testing). In the third phase, we conduct two summative evaluations to assess the impact of the adjusted program and design principles. We investigate the perceptions and behavior of both teachers and parents. In this phase, researchers keep more distance (i.e., gamma testing) and systematically evaluate the outcomes of the program by applying data triangulation (George & Bennett, 2005; Yin, 2018). In the fourth phase, we reflect on the design principles and their theoretical implications to further refine the design (Plomp, 2009). This research process aims at generating general design principles (Andriessen & Van Aken, 2011) that contribute to improved partnerships between teachers and parents, connecting environments for children to become at home in language . THIS THESIS This thesis presents four studies. They are structured by a stepwise design process (see Figure 1.1) and were conducted between January 2012 and December 2015. The first study (Chapter 2) extracts effective activities and strategies for language promotion by lower-educated parents through a systematic review study. This study is used to acquire specific pedagogical knowledge for teachers to support lower-educated parents. The second study (Chapter 3) examines the tentative design principles by iteratively testing the initial prototype of the AHL program and making consecutive formative evaluations. The third and fourth studies (Chapters 4 and 5) investigate the outcomes of the adjusted design by assessing the enactment of teachers and parents, considering teachers’ abilities to reliably convey the content of the program as intended. Study 3 is a summative evaluation of teachers’ perceptions of working with the AHL program and consists of observations of behavior when applying its design principles with parents and children in classrooms. Study 4 is a summative evaluation of parents’ perceptions and behavior of the AHL program during their enactment of design principles with children in the classroom. The final chapter (Chapter 6) systematically evaluates the design principles and the theoretical and practical implications of the program.