Michael Thier proposes that in a world beset by the opportunities and challenges of globalization, Global Citizenship Education (GCE) can instill the knowledge, skills, behaviors, and dispositions to live, learn, and work. In one of many global citizenship conceptualizations, Oxley and Morris (2013) present four cosmopolitan dimensions--political, moral, economic, and cultural--and four advocacy dimensions--critical, social, environmental, and spiritual. Thier argues that with so many dimensions to navigate, one might readily recognize why GCE can prompt students' critical thinking about the world they inhabit (Henderson, Nunez-Rodriguez, & Casari, 2011; Maguire, Donovan, Mishook, de Gaillande, & Garcia, 2012). Thier writes that given climate change, wealth inequality, permeable borders, and complex geopolitical conflicts, it seems logical that GCE would be offered as a public-school standard. Unfortunately, though, the travesty of inequitable opportunities to learn relegates GCE to boutique status. Less than 1.5% of U.S. public schools offer GCE to their K-12 students (Thier, 2016). Even in the rare places that offer GCE, access favors students who are university-bound, white, and from affluent backgrounds (Perna et al., 2013). Several additional challenges thwart efforts to scale up GCE: Its literature base is diffuse (Marshall, 2011), its definitions remain hotly contested (Davies, 2006; Myers, 2016), and empirical studies are rare (Kerkhoff, 2016). Thier concludes that still, this burgeoning area of interdisciplinary research and practice links GCE to several desirable outcomes, such as increasing empathy within and across cultures, as well as fostering engagement with and understanding of complex international affairs (Goren & Yemini, 2017).