Building from findings showing that undergraduate computer science continues to have the highest attrition rates proportionally for women within postsecondary science, technology, engineering, and mathematics disciplines--a phenomenon that defies basic social equity goals in a high status field--this paper seeks to better understand how student experiences in local higher educational settings can influence persistence decisions, particulary for women. Updating and extending work in computer science, our qualitative analysis interprets this wider problem, first, by applying a field theory of practice to more clearly theorize how varying social realms and positions influence student experiences and feelings of belonging. Second, we use an in-depth comparative case study of two introductory or "gateway" computer science courses in two universities to detail how classroom, departmental, institutional, and extra-institutional characteristics, including instructional practices and popular stereotypes, may shape action for students in specific higher educational contexts. While previous studies have highlighted the significance of broader computer science cultural values, self-efficacy beliefs, and experience with computers to women's attrition, our findings provide a new theoretical lens to conceptualize the complex ways these and other factors connect in students' daily lives--through preening male students or "brogrammers," authentic or collaborative learning experiences, and uncomfortable social interactions due in part to women's underrepresentation. Our findings also point to differences in local interactions and social positions that can begin to mediate these factors, including opportunities in class to ask questions, collaborate, and work on real-world example problems; fuller access to instructors; and departmental and campus infrastructural supports that contribute to a more meaningful sense of belonging in computer science.