Background: Current reforms in K-12 STEM education call for integration between science, technology, engineering, and mathematics (STEM). Such integration of STEM disciplines at the K-12 level offers students an opportunity to experience learning in real-world, multidisciplinary contexts; however, there is little reported research about teachers' experiences in engaging in integrated STEM instruction. The purpose of this phenomenological multiple case study is to understand nine science teachers' first-time experiences in implementing integrated STEM curricular units in their middle school physical science classrooms. This study draws upon both classroom implementation data and teacher reflective interviews to illustrate different degrees of integrated STEM instruction and to understand teachers' challenges and successes with these varying approaches. Results: Our results indicate three distinct cases of integration within our sample that represent low, medium, and high degrees of STEM integration throughout curriculum implementations. Interviews with teachers from each case revealed three themes that varied across teachers' experiences: the nature of integration, choosing between science and engineering, and student engagement and motivation. Teachers in all three cases were challenged to make explicit connections between science, engineering, and mathematics while simultaneously maintaining a motivating and engaging context for their students throughout their instruction. Further, it appears that the degree of STEM integration that occurs in instruction may be related to teachers' ability to make explicit connections between the disciplines.

Given the large variation in conceptualizations and enactment of K− 12 integrated STEM, this paper puts forth a detailed conceptual framework for K− 12 integrated STEM education that can be used by researchers, educators, and curriculum developers as a common vision. Our framework builds upon the extant integrated STEM literature to describe seven central characteristics of integrated STEM: (a) centrality of engineering design, (b) driven by authentic problems, (c) context integration, (d) content integration, (e) STEM practices, (f) twenty-first century skills, and (g) informing students about STEM careers. Our integrated STEM framework is intended to provide more specific guidance to educators and support integrated STEM research, which has been impeded by the lack of a deep conceptualization of the characteristics of integrated STEM. The lack of a detailed integrated STEM framework thus far has prevented the field from systematically collecting data in classrooms to understand the nature and quality of integrated STEM instruction; this delays research related to the impact on student outcomes, including academic achievement and affect. With the framework presented here, we lay the groundwork for researchers to explore the impact of specific aspects of integrated STEM or the overall quality of integrated STEM instruction on student outcomes.

It is difficult to ignore the increased use of technological innovations in today's world, which has led to various calls for the integration of engineering into K-12 science standards. The need to understand how engineering is currently being brought to science classrooms is apparent and necessary in order to address these calls for integration. This multiphase, mixed-methods study investigated the classroom practices and beliefs of high school physical science teachers following an intensive professional development on physics and engineering integration.Classroom observations showed that teachers new to incorporating engineering into their physical science classrooms often struggled to maintain focus on physics concepts, focusing instead on the development of the ''soft skills'' needed by engineers, such as teamwork or communication. Interviews and surveys further revealed the beliefs of these teachers when considering integrating engineering into physics lessons. Teachers placed student engagement and enjoyment high on their priority list when considering integrating engineering into their classroom. In addition to this somewhat driving force, three main components were identified as important when considering engineering in physical science classrooms: providing hands-on experiences for students, allowing students to apply physics concepts, and developing general problem solving skills that students can take to the ''real-world.'' While teachers identified both physics and engineering goals for their students, they realized that their students learned more about how to be an engineer.Results from this study provide insight on obstacles current science teachers face as they begin to add engineering to their classrooms. Overall, teachers are motivated to bring engineering to their classrooms as a result of student enjoyment of engineering activities. This may drive the creation of teacher goals for students and determine how emphasis is placed on different goals during these engineering design challenges. Implications for this study include ascertaining knowledge about teacher beliefs prior to professional development, fostering discussions about what integration looks like in the classroom, and modeling the creation of instructional goals that include both physics and engineering content.

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