In the global economy that is intertwined with scientific and technical knowledge and innovation, raising a Science, Technology, Engineering, and Mathematics (STEM)-literate generation of students has emerged as one of the paramount goals of most countries. Educational models that contribute to meeting those countries' goals have become important in education. The absence of standards-focused, ready-to-teach teacher and student materials and lack of regular teacher trainings are some of the barriers attributed to the current STEM teaching approaches. Against this background, we investigated a successful STEM teaching model that has ready-to-teach materials, standards-focused, regular teacher professional trainings and student choice and voice that utilize both classroom and out-of-classroom projects as a solution to the aforementioned issues. The purpose of this research is to examine a new STEM teaching approach developed by a public charter school system, Harmony Public Schools (HPS). We used theoretical sampling; 11 semi-structured interviews were conducted with high school students. Grounded theory and constant comparative analysis were utilized. Study findings have revealed that the students were active learners most of the time, presenting and sharing their findings with classmates and visitors. Thus the title of this research, STEM Students on the Stage (SOS), is used to describe this model. In addition, emerging substantive theory suggested that STEM SOS model helped students learn STEM subjects better, cultivate STEM subject interests, and develop skills for their college and professional lives. Implications of the effect of this model on K-12 students' learning experiences are discussed in detail. Scientists, technologists, engineers, and mathematicians are high-tech workers who have the knowledge to turn the wheel of the global economy (Craig, Thomas, Hou, & Mathur, 2011). Accordingly, the importance of science, technology, engineering, and mathematics (STEM) education cannot be underestimated for countries in an innovation-driven economic world (Top & Sahin, 2015; Sahin, Ayar, & Adiguzel, 2014; Sahin, 2013). Several reports have highlighted the links between a well-rounded K-12 STEM education - to prepare the next generation's scientists, leaders, and innovators - and countries' economic leadership (e.g., National Academy of Sciences, 2007; President's Council of Advisors on Science and Technology, 2010). Yet statistics show that there is a disproportionate growth in terms of numbers and quality of STEM workers (Mahoney, 2010; Lacey & Wright, 2009). Thus, developing a quality STEM education that prepares students for the 21st century workforce becomes paramount for each country'seconomic wellbeing. For this purpose, different approaches have been pursued to teach STEM subjects in K-12 settings. Some of the research-based methods for interdisciplinary STEM education are Design- Based Science (DBS) (Fortus, Krajcikb, Dershimerb, Marx, & Mamlok-Naamand, 2005), Math Out of the Box™ (Diaz & King, 2007), Learning by Design™ (LBD) (Kolodner, et al., 2003) and Integrated Mathematics, Science, and Technology (IMaST) (Satchwell & Loepp, 2002), all of which incorporate a course of inquiry-based learning that encourages students to complete a project with respect to existing knowledge and experience, and to present what they learned and developed as a result (Laboy-Rush, 2011). For the most part, each method provides students a four- or five-step process, with each step accomplishing a specific process-based objective. Similarly, the project-based learning strategy has been found and proven to be an effective STEM education program (Laboy-Rush, 2011). These methods are successfully implemented because of the models' integration of cooperative learning, working in teams to do research, testing theories and producing artifacts (Meyrick, 2011). Harwood and Rudnistsky (2005) indicated that such teaching and learning methods increase students' involvement and engagement, and "can stimulate students as well as enable them to recognize links between their lessons and tasks performed by engineers in the real world" (p. 54). However, there have been some gaps in the implementation of current conventional PBL models (Mapes, 2009; Marx et al., 1997), namely, a) teachers don't have access to ready-to-teach materials including teacher guides, student handouts and assessment materials; b) there is a lack of regular teacher trainings; and c) non-aligned PBL lessons that don't prepare students for standardized testing. In this study, we investigate a new STEM PBL teaching approach that incorporates a full curriculum, including ready-to-teach teacher materials, PBL projects for all core subjects, regular teacher trainings and aligned with multiple state standards. [ABSTRACT FROM AUTHOR]