The aim of the research was to find out the effectiveness of collaborative learning to teach descriptive writing at senior high school.
The research used experimental method. The population of this research was the tenth grade students on one of the senior high schools in Banyumas which consists of 280 students. The random sampling was chosen to get the sample of the research. Class X7 was chosen as control class and X8 as experimental class. This research was carried out from March 21st to April 11th 2012.
After doing the research, the experimental class had shown the positive changes of students’ achievements. The improvement was on the students’ activity using CL and the elements of writing i.e. on the content of writing, structure of writing, and writing mechanics.
After the data had been analyzed, the t-test computation was 3.110, and t-table for df=64 at the level of significance α=0.05 was 1.669. From the previous calculation, the t-test was higher than t-table (3.110>1.669). Thus, the hypothesis was accepted or it means that collaborative learning was effective in teaching English writing particularly descriptive writing.