The aim of the research was to find out the effectiveness of cluster technique to
teaching writing of descriptive text at senior high school. This research was quasi
experimental method. The population of this research was the tenth grade on one of
the senior high schools in Yogyakarta which consists of 245 students. The students
involved in the research were 70 students who were divided into two classes. The
subjects of the research were class XA-6 with 35 students as experimental class and
XA-7 with 35 students as control class. The technique of collecting the data was by
using tests (pre-test and post-test). The type of the test was subjective test where the
students had to compose some sentences. The data calculation showed that there was
a positive impact of teaching writing of descriptive text. It can be seen from the mean
score result of experimental class had impact or increased 14.40 point from the pretest
59.60 to the post-test 74.00. whereas, the mean score in the control class had
increased 8.73 point from pre-test was 57.26 to post-test was 65.96 and based on the
result of t-test computation was 4.473, and t-table for df=68 at the level of
significance α=0.05 was 1.668. From this calculation, the t-test was higher than ttable
(4.473>1.668). Thus, the hypothesis was accepted or it means that clustering
technique was effective in teaching writing particularly descriptive text.