摘要：The research aims at improving students’ writing skills using collaborative learning at 10th-grade students of the Senior High School 1 of Veteran Sukoharjo. This research was a classroom action research. The technique used in this research consisted of planning, implementing, observing and reflecting. The research was applied in two cycles. Every cycle consisted of three meetings. In the technique of collecting data, the researcher used qualitative and quantitative techniques. The qualitative data were collected from documentation, observation and interview with teachers and some students. The quantitative data were collected from the score of the students’ pre-test ad post-test, validity and reliability. The result of the research showed that collaborative learning could improve students’ writing skills. By using collaborative learning, the students showed active and have self-confidence in the teaching-learning process. This method brought positive result. The progress of the students’ writing skills also can be seen from the result of the tests score. In the multiple-choice pre-test, the mean score of the pre-test was 59,7and improved to be 68,1in post-test 1 of cycle 1. In cycle 2, the mean score of post-tests 2 was 79,7. In the essay pre-test, the mean score of the pre-test was 61,3and improved to be 69,1in post-test 1 of cycle 1. In cycle 2, the mean score of post-tests 2 was 78,4. It could be concluded that there was a significant improvement in the students writing skills after using collaborative learning.
