Quality in early care and education (ECE) has been widely studied across several decades. There is not one standard definition of quality across ECE contexts. However, classroom quality often encompasses both structural features of quality, such as teacher-child ratios and teachers' qualifications, and process features of quality, such as teacher-child interactions and the climate of the classroom environment. Yet, teachers are often not included in discussions about quality and accountability measures used in ECE programs. This study used an explanatory sequential mixed methods approach to understand teachers' perceptions of classroom quality and accountability tools used in Head Start. The Classroom Assessment Scoring System (CLASS) is a widely used measure of process quality in ECE settings and has been adopted by Head Start as a high stakes accountability tool. This study examines the following research questions: 1a) Are teachers' demographic characteristics and roles associated with their opinions of indicators of quality in Head Start? (QUAN); 1b) To what extent do Head Start teachers believe CLASS scores and quality thresholds are an accurate representation of the quality of their classroom? (QUAN); 2a) How do Head Start teachers define quality? (qual); 2b) What are Head Start teachers' opinions of the CLASS as an accountability tool? (qual); 3a) Do features of quality in Head Start align with teachers' definitions of quality?; and 3b) Do definitions of quality provided by Head Start teachers align with the CLASS's definition of quality? The findings from this study build on prior work and suggest further research is needed to incorporate teachers' perceptions in discussions about policies that regulate quality in Head Start. [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.]