The purpose of this qualitative descriptive case study was to determine the prevalence of principal mistreatment or bullying and its association with teacher morale and teacher effectiveness in the classroom. The study focused around one central research question: What is the prevalence of principal mistreatment or bullying? Two sub questions framed the qualitative descriptive case study: (1) What is the impact of principal mistreatment or bullying on teachers' morale? (2) How does principal mistreatment or bullying impact teacher effectiveness in the classroom? Thirty-five certified teachers participated in this research study by completing the online questionnaire and survey. Twenty of the thirty-five certified teachers participated in a personal interview. Data was collected through an online questionnaire, an open-ended online survey, and voluntary personal interviews. NVivo 9 was used to code and analyze the data. Two major themes were derived from each of the framed research questions. The first framed research question relating to the impact on teacher morale produced the theme of favoritism, low morale and lack of motivation. The second framed research question relating to the impact on teacher effectiveness in the classroom produced the theme of isolating and abandoning teachers and loss of adequate support and the theme of less confidence in teaching ability and skills. Both framed research questions produced a fifth theme of criticism. The findings of the research study established that principal mistreatment or bullying still needs to be addressed. Implications and recommendations for leadership development in professional ethics and interpersonal skills are included for future research to address the findings of the study on the problem of principal bullying impacting teacher's ability to perform effectively in the learning environment.