Object This study conducted an 8-week experiment with the basketball sports intervention program to explore the relationship between the basketball sports intervention program and the physical self-esteem and school adjustment of first-year high school students, providing references for first-year high school students’ school adjustment and related research. Methods Using convenient sampling,88 students in two classes of grade one in a senior high school in Changzhou were selected as the experimental research objects and were randomly divided into experimental groups (basketball) 44 people (20 male and 24 female; control group routine physical education) 44 people (23 male and 21 female). The exercise intervention lasted 8-week, 3-times-a-week with about 30 minutes of moderate-intensity exercise each time. The control group had normal sports activities, and the exercise intensity was not monitored. The Physical Self-esteem Scale and the School Adaptation Scale were used to measure the data in a group manner before and after the experiment. All data were statistically analyzed with SPSS26.0. Results (1) After 8 weeks of basketball intervention, the post-test level of school adaptation of first-year high school students was significantly higher than the pre-test (p < 0.01), and the post-test level of physical self-esteem was significantly higher than the pre-test (p < 0.01). (2) Basketball intervention can directly affect the school adaptation of first-year high school students and indirectly affect the school adaptation through physical self-esteem. The direct effect was 86.79%, and the indirect effect was 13.21%. Conclusion (1) Intervention of moderate intensity basketball can improve first-year high school students’ school adaptation and physical self-esteem. (2) Intervention of moderate intensity basketball can directly improve first-year high school students’ and school adaptation by improving individual physical self-esteem. Physical self-esteem plays a partial intermediary role between basketball and school adaptation.