Multiply marginalized learners (MMLs), students with two or more marginalized identity factors (Annamma et al., 2013), are America's most vulnerable K-12 student population. MMLs face significant challenges, including increased opportunity- and academic achievement gaps (Hanushek et al., 2019; McClellan et al., 2018). They are disproportionately referred for special education services (Abou-Rjaily & Stoddard, 2017; Hallahan et al., 2020) and are likelier to drop out of school (Bridgeland et al., 2006; Doll et al., 2013). Moreover, these challenges have long-term implications on postsecondary life, such as lower college attendance, higher incarceration, lower instances of marriage, higher instances of divorce, income inequality, poor health, lack of access to healthcare, and overall poor quality of life (Hanushek et al., 2019; McKinsey & Company, 2009; Sanford et al., 2011; US Chamber of Commerce, 2020). In this single instrumental case study, I examined four urban special educators' implementation of dis/ability critical race theory (DisCrit; Annamma et al., 2013) and the five dimensions of multicultural education (MCE; Banks, 1993a) frameworks in their instruction to improve the academic experiences and postsecondary development of MMLs. I analyzed data from four semi-structured interviews and one focus group session. According to the findings, critical consciousness and critical thinking skills were foundational to fostering MMLs' academic engagement and self-efficacy. Additionally, critical consciousness was essential to MMLs' transition into postsecondary life. Moreover, participants centered the culture, prior knowledge, and lived experiences of MMLs to create equitable and meaningful learning experiences. This practice was another method for improving MMLs' academic outcomes. Furthermore, findings indicated that participants helped MMLs define and value their identities. Two additional findings emerged from the study: the significance of building relationships with MMLs to support their academic and postsecondary growth and the positive impact of holding high expectations of MMLs. A lack of data demonstrating participants' implementation of activist and resistant forms of teaching also emerged. This study focused on urban special educators, leaving a void in understanding how DisCrit and the five dimensions of MCE impact MMLs' academic experiences and postsecondary outcomes from the perspective of these students. Future research with MMLs as participants is needed. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]