ABSTRACTThis research aims at: (1) identifying whether and to what extent Student Teams-Achievement Division (STAD) method improves students’ reading skill, and (2) describing the class climate when the teacher implements Student Teams-Achievement Division (STAD) method in reading activity.This research has been implemented in one cycle to the tenth grade students of SMA Negeri 1 Karanganyar in the second semester of the academic year 2014/2015. The research data were collected by using qualitative and quantitative techniques. The qualitative method consisted of observation, field notes, interview, diary, and photograph. The quantitative data were analyzed by comparing the mean score of pre-test and post-test.The results of this research showed that students’ skill in identifying explanation text had improved and the changes of classroom climate became more motivating. The improvement in students’ reading comprehension includes: 1) students could identify main idea based on text; 2) students could infer communicative purpose of the text; 3) The students could identify explicit information based on the text; 4) The students could identify implicit information based on the text; 5) students could understand word meaning; 6) students could identify the referents of the pronoun found in the text. The final result of the tests showed that their scores were improving in the mean score; from 71.5 (pre-test) to 83 (post-test). It was above the minimum standard of the school (Kriteria Ketuntasan Minimuml/KKM), which is 75.00. Related to the improvement in the class climate, the research findings showed that 1) Students give more attention to teaching learning process; and 2) Students tend to be active learners in the classroom. Besides two findings above, there are improvements of the students learning activity includes: 1) Students enjoy and get interested in the classroom situation; 2) All students are involved in the teaching learning process; 3) Students solve the problem by discussion and share their idea.Keywords: reading, student teams-achievement division, reading skill, senior high school students