Teachers play an important role in student learning. When teachers are assigned to teach outside their expertise, it can prove challenging for them. This dissertation is a step towards understanding how different out-of-field conditions impact science teachers. The first study of the dissertation aims at understanding the development of enacted pedagogical content knowledge (ePCK) of early career teachers teaching out-of-field in their instructional area. The study participants are 17 teachers teaching physical science as a part or all of their teaching assignments during the first three years of their teaching career. Data for this study were collected in the form of classroom observations and semi-structured interviews. The findings from this study indicate that teachers teaching out-of-field show less developed ePCK and show more inconsistencies in their PCK than their in-field counterparts. This study highlights that OOF teachers do not build their instructional practices at the same rate as their in-field counterparts and the need to support teachers teaching outside their expertise. In thinking about supporting science teachers, the second study focuses on being OOF in the area of context. This study is focused on understanding the shifts in the knowledge, practices, and attributes of science coordinators and the resources they draw upon in supporting science teachers during the pandemic. The participants in this study are 15 science coordinators from ten countries. The data for this study consists of semi-structured interviews and follow-up interviews if needed. This study uses the concepts of organizational resources and capital as the framework to understand the experiences of school science coordinators. This study indicates an increase in technology (that was essential for the shift), collaboration, creativity, and interpersonal skills. The majority of the practices and attributes that were important during the pandemic were related to working with people (soft skills). SCs' knowledge, practices, and attributes translated as supports in the form of social and material resources and likely human resources available to the teachers. This study highlights how science coordinators can support teachers as they are out-of-field in their instructional context. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]