In the recent years, Tanzanian government secondary schools’ managerial ethics have been declining leading to deduction of internal efficiency. This study sought to; identify school managerial ethics that influence internal efficiency; to identify school managerial dilemmas that hinder internal efficiency of a school and to identify strategies for improving schools managerial ethics. The study was conducted in Musoma municipality involving 4 school heads and 68 classroom teachers from four government secondary schools. To achieve the purpose of this study a mixed approach, which utilized explanatory design was used, and data was collected through interviews, questionnaires, and non-participant observations. The findings indicated that some school’s managerial ethics which influence internal efficiency of a school, like the use of school policies and priorities for development projects, whereas on the other side, school malpractices like teachers’ and students’ absenteeism; little handling of complaints; student love affairs just to mention a few, sought to have reduced efficiency of schools. Findings imply that, the Ministry of education and Vocation Training (MoEVT) should regularly provide on-job and off-job training; heads of school need to create and enforce discipline at their work place; and that, classroom teachers should not have great dreams, which are above their earning capacity. It is concluded that, with positive schools’ managerial ethics internal efficiency will be obtained and the vice versa is correct. Furthermore, the study recommended for the similar study to be conducted in other parts of Tanzania due to the fact that Musoma municipality cannot generalize many other regions of Tanzania, which vary in their geography, history and economic development.