This study was aimed at finding out: (1) whether there is a significant difference in writing skill between students taught using Collaborative Writing and those taught using Interactive Writing; and (2) whether Collaborative Writing is more effective than Interactive Writing to teach writing. The research method used in this study is a quasi-experimental research design. This research was conducted at MAN Klaten in the academic year of 2016/2017. The population of the research is the tenth grade of MAN Klaten. The samples are class X IPA 6 as the experimental class which consists of 34 students and class X IPA 5 as the control class which also consists of 34 students. The research instrument used to collect the data in this study is a test. The data were analysed by using t-test formula. The computation of the t-test shows that t observation (to) = 4.594 is higher than t table (50, 0.05) = 1.996. Therefore, it can be concluded that there is a significant difference in writing skill between the students taught using Collaborative Writing and those taught using Interactive Writing. The mean score of experimental group is 72.47, while the mean score of control group is 61.41. Therefore, it can be concluded that Collaborative Writing is more effective than Interactive Writing to teach writing.Key words: collaborative writing, interactive writing, writing skill