The Self-Determination Theory posits that an autonomy-supportive motivating style can benefit students in numerous educationally important ways. The paradox and educational concern is that although teachers are cognizant that students can reap numerous benefits when they support their students' autonomy, many of them are nevertheless unable to do so. This can be explained by the implicit and explicit forces imposed on them from their external and internal environments. This paper investigated the school-related factors that affect teachers' adoption and employment of autonomy-supportive motivating style. To achieve the objective, we interviewed 59 mathematics and/or science teachers (M[subscript years of teaching] = 10.8, 62.71% female) from 17 secondary schools in Singapore. We identified several school-related factors that could affect the teachers' motivating styles, namely, "time pressures", "support from school leaders", "support from colleagues" and the "time of the year (timing)". Because autonomy-support is important for students' motivation and learning, a better understanding of the school-related factors that affect the teachers' motivating style would be helpful in creating a context that allows the teachers to be more supportive of their students' autonomy.