According to the National Center for Educational Statistics (NCES), minority populations are increasing significantly and are predicted to become the majority nationwide by 2024 (Kena et al., 2015). Frankenberg & Orfield (2012) explain that suburban schools are struggling with the realization that their schools are more racially/ethnically and socio-economically diverse. Further difficulties arise when teachers see race, ethnic or socio-economic differences from a deficit point of view, one where a child's culture, home life and perspectives are viewed negatively (Terrell & Lindsey, 2009). Lack of cultural understanding leads educators to underappreciate family and cultural belief systems as well as academic potential of minority students (Nelson & Guerra, 2014). As a result, districts are failing to close the achievement gap that exists between white students and minority students and students in poverty (Ladson-Billings, 2006). Extended training in culturally responsive teaching is necessary to shift a deficit mindset to one of full appreciation and advocacy for what students' race and socio-economic status add to the classroom (Ebersol, Kanahele-Mossman & Kawakami, 2015; Terrell & Lindsey, 2009). The purpose of this qualitative study is to explore the role of professional learning in developing cultural proficiency among teachers and building leaders and its impact on instructional practices that are responsive to the needs of racially and ethnically diverse student groups and students of poverty. Through the lens of cultural proficiency (Terrell & Lindsey, 2009), and Learning Forward Standards for Professional Learning, (Mizell, Hord, Killion & Hirsh, 2011) the researcher used a phenomenological approach to research and conducted interviews with a district administrator/coordinator of professional development, a principal, eleven teachers (elementary and/or middle school and/or high school) in three suburban districts in upstate New York. The findings of this study reveal that professional development was aimed at increasing educators' sensitivity and responsiveness toward English Language Learners, special education students, people of color and families living in poverty. Interview narrative revealed that these districts adhered to most tenets of the Learning Forward Standards for Professional Learning by partnering with teachers to develop job embedded, ongoing professional development offered in a variety of formats with internal and external expertise. Educators in these suburban districts, trained in cultural proficiency, were dedicated to increasing the likelihood of school readiness and creating opportunities to share and celebrate cultural differences. All three districts plan to continue to provide professional development that breaks down implicit bias, provides best practices for low SES students, special education students and ELLs. [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/en-US/products/dissertations/individuals.shtml.]