This study was aimed at finding out the level of determination of managerial ability, principal's motivation and teacher's professionalism toward the quality of instruction of teachers at SMAs in Sukasada district. This study belongs to ex post facto research. The population consisted of 43 teachers and the sample size was 40. The data were collected through an administration of questionnaires that have been tested in terms of validity and reliability and the hypotheses testing was done by using simple regression, multiple regression and partial correlation. The results showed that managerial ability had a significant effect on quality of instruction (38.5% determination), principal's motivation had a significant effect on quality of instruction (41.0% determination), teacher's professionalism had a significant effect on quality of instruction (56.5% determination). The conclusion of this study is that managerial ability, principal's motivation, and teacher's professionalism are strategic factors in the creation of professional quality of instruction at SMAs in Sukasada district with 65.0% contribution. It is suggested that if the principal would like to create professional quality of teacher's instruction, he or she should select an appropriate management, giving the teachers motivation and education and training on structured and sustainable teacher's professionalism.