This study will evaluate the effectiveness of a teacher performance assessment model. Teacher performance is a timely subject and very much of interest to educators, policy makers and the general public. The Stallings Observation Instrument (SOI) will be utilized to assess the performance of teachers. It has not been studied to date in that context. The design of this study will be experimental research. A total of sixteen (16) vocational teachers will be observed by certified coders using the Stallings method. Eight (8) vocational teachers will serve as the control group. After the initial observation, eight (8) vocational teachers will receive a developmental treatment and a second observation will be conducted. An analysis of covariance will be utilized to provide an analysis of the data and a comparison of the performance of the groups. The results of the study will provide data and data interpretation on the effect of the Stallings Observation Instrument (SOI) on the teacher performance assessed. / Ed. D.