PBL is experiencing renewed attention in the educational landscape. Researchers have defined PBL in a variety of ways over the years. The Buck Institute for Education [26] defines PBL as “a teaching method in which students learn actively by engaging in real world and personally meaningful projects” (np). Wilhelm et al. [3] examine the role of the teacher in PBL, noting the importance of instructional milieu in successful project-based endeavors. Across various conceptions of project-based approaches, core features include: (1) a challenging problem or question [3,27]; (2) student voice and choice; (3) authentic community engagement; (4) benchmark lessons/activities [28]; (5) reflection, critique, and revision [26]; and (6) public product.

One of the long-standing premises drawn from a Deweyian perspective is that PBL, as a contemporary example of learning by doing, increases student motivation [29,30]. Research focused on the student outcomes of learning through project-based approaches is promising in terms of academic content knowledge as well [31]. One study of high school students with teachers who participated in the Buck Institute PBLWorks professional learning demonstrated statistically significant growth in reading, math, and history when compared to peers whose teachers did not participate in professional learning [32]. As the most definitive experimental study of PBL to date, Duke et al. [33] conducted a cluster randomized control trial of second-grade students engaged in PBL in which students demonstrated higher growth in social studies content and informational reading. Although this study took place with elementary students, it demonstrates that PBL can result in student learning gains as opposed to just motivational gains as other studies have demonstrated. Moreover, Craig and Marshall [34] found, through a randomized control study of secondary students at a nationally recognized model STEM school, that students taught through PBL matched the performance of conventionally taught students for the 11th-grade science and 9th-, 10th-, and 11th-grade mathematics achievement measures and exceeded the conventionally taught students’ performance for the 10th-grade science achievement measure.

A limitation in the literature is how PBL can be implemented collaboratively across school sites. In their metasynthesis of PBL, Minner et al. [20] found that only 6% of PBL studies (8 out of 138) encompassed multiple settings. In this study, we examine student motivation and science content knowledge outcomes throughout a cross-school PBL collaboration, using PBI Global.

As a type of PBL, PBI Global has a defined, five-phase, collaborative inquiry cycle and focuses students’ research on one or more of the UN Sustainable Development Goals (SDGs). An impact-driven pedagogy, PBI Global alters traditional classroom instruction through a hands-on, minds-on approach to learning, encouraging students to make sense of their world, locally and globally, through inquiry.

PBI Global Cycle. PBI Global has five phases (see Figure 1), including composing a compelling question, gathering and analyzing sources, creatively synthesizing claims and evidence, critically evaluating and revising research findings, and finally, communicating (i.e., share, publish, and act) learning products to a larger audience. Typically, prior to developing compelling questions, students engage in background knowledge building by reading a narrative or informational text. PBI Global has three distinguishing inquiry cycle features that differentiate it from other models of inquiry-based learning, such as the 5Es instructional model [35], the C3 Teachers Inquiry Design Model [36], and the International Baccalaureate inquiry process [37]. Those features are (1) a focus on the UN Sustainable Development Goals as the framework for learners’ solutions-oriented inquiry; (2) an interdisciplinary approach to the inquiry cycle; and (3) an explicit call for students to take social action as a result of their inquiry findings.