Background: School principals usually have to sacrifice health and family obligations to obtain sufficient work time. This study investigates school principals' somatic and psychological discomfort related to their time allocation to diverse work contexts and life domains, so as to test the optimal allocation of time to each context and domain. Methods: This study is based on survey data of 347 school principals, from the preexisting 2021 Survey of School Teachers' Living Conditions in Shanghai. Generalized linear regression modeling was adopted to analyze the data according to the research purpose. Results: This study finds that school principals' daily time spent on work at home, sleep, breakfast, exercise, and family obligations significantly predict their somatic or psychological discomfort. However, their time spent on work at school, daytime napping, lunch, and dinner are not of significance. Conclusions: This study reveals several unhealthy ways of working and lifestyle habits among school principals from a perspective of time allocation, such as extended periods working at home, sleep deficits, hurried breakfast, lack exercise, and failure to meet familial obligations.