Previous research on belonging in computer science offers insights into the role that stereotypes play in reducing females’ sense of belonging or fit in computer science (CS), which has been associated with their significant underrepresentation in the field. Drawing upon mixed methods (surveys and interviews), this study explores the quantitative variables associated with a sense of belonging for females in high school CS courses and provides qualitative insights from students to help explain why these factors matter. Pre/post survey analysis indicates that the courses are contributing to reducing pre-course gender gaps in students’ perceived efficacy and belonging in a CS classroom. The surveys also suggest that females were more engaged and developed stronger relationships with teachers. And yet, females’ commitments to continuing with CS had no statistically significant changes. Student interviews provide important context regarding the quantitative findings and describe how positive relationships with a female teacher, collaborative work and inclusive teaching practices played key roles in promoting a classroom sense of belonging for females. Overall, these results suggest that an academically engaging and socioemotionally supportive experience in a computer science course can reduce gender gaps and foster females’ sense of belonging in the classroom even if they retain some reservations over their long-term fit in the field. The findings contribute to a more nuanced understanding of the factors that promote equitable experiences for females in CS and the relationship between classroom level belonging and long-term fit in computer science.