Self-efficacy can determine how hard a student works, if they will persevere in the face of obstacles or succeed academically (Britner & Pajares, 2006). It has been suggested that practices in an inquiry-based science class can provide positive experiences needed to increase self-efficacy of middle school students (Britner & Pajares, 2006). Middle school (ages 11-14) is a time when students' attitudes toward science have been shown to change (Gibson & Chase, 2002). Inquiry-based science is not always utilized in middle school and studies have shown that the way science is taught may be linked to teachers' self-efficacy (Menon & Sadler, 2016; Appleton, 2007). Through mixed-methods research, the self-efficacy of students in middle school was investigated while studying the environment in which they learned. Surveys, classroom observations, and an analysis of teaching activities, gave insight into the teaching styles and inquiry-levels utilized by two teachers, at different schools. A student questionnaire was developed to track students' self-efficacy over a semester. Inquiry-based science was found in both classrooms, but utilized more in the classroom of the teacher who reported feeling a higher level of preparedness. Students learning in the more collaborative, inquiry-based environment saw increases in their self-reported self-efficacy scores. Gender differences were also evident. Further studies are needed to examine if these changes are significant or would occur over a longer period of time. [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.]