The purpose of this study is to investigate relationships between students' engagement versus disaffection and their perceptions of teachers' motivational support styles. To do this a hypothesized structural model specifying the direct relationships of students' engagement and their perceptions of teachers' motivational support is used. The model, covers students' motivational regulations, as mediator variables, between students' engagement and their perceptions of teachers' motivational support styles, that is tested. Participants are 276 ninth grade high school students (148 girls and 126 boys). Data are collected by the "Effective Participation Scale," "Motivational Regulation Scale," and "Teachers' Motivational Support Scale." The fit statistics indicate that the research model provides a reasonably good fit to the data (x[superscript 2] = 74.62, df = 38, p = 0.00, RMSEA = 0.086, RMR = 0.05, CFI = 0.96, GFI = 0.90, AGFI = 0.92, NFI = 0.91, NNFI = 0.91). Chi-square to degrees of freedom ratio x[superscript 2]/df = 1.96 is satisfactory. The study indicates that motivational support provided by teachers has effect on the students' motivation orientation and active class participation.