This study was chosen to identify the effectiveness of self-assessment
technique in improving students‟ English speaking achievement, particularly in
teaching speaking. It could be done especially for the senior high school students
from RSBI (International Standard School Candidate). It was selected to be
investigated because speaking was difficult for the students to be done. The
respondents were the students in Ajibarang state senior high school. XI.IS.1 as the
experiment group and XI.IS.3 as the control group. It consisted of 68 students. It used
purposive cluster sampling in getting the sample. The instruments used in this study
were tests and questionnaires. It used t-test and inter-rater reliability as a tool to
analyze the data. It was carried out from January until February 2012. The result was
higher than t-table. It was 2,292, and the result of t-table at significant level 0,05 with
the degree of freedom 58 was 1,672. Then, the calculation of t-obtained with t-table
was concluded that t-obtained was higher than t-table (2,292 > 1,672). It could be
seen that self-assessment technique was effective to improve students‟ English
speaking achievement in teaching speaking.