This thesis is entitled "The Influence of Learning English at Elementary School to Get Good Writing Performance of Junior High School Students." (a case study at SMPN I Jantho). The aims of doing this research are to answer whether there are any differences between the students who have learned English at elementary school and those who have never studied in mastering writing skill and to know whether or not the students who have studied English at elementary school are better in writing skill than those who have never studied it. The population of this study was the second year students of SMPN 1 Jantho. The sample of this study was two classes of the second year students. The total numbers of the sample were 68 students. The data of this study were collected on February 19" and 23", 2007. The method applied in this study was descriptive quantitative analysis. The instrument used was test. This test consisted of 25 questions related to writing skill. The data of this test was analyzed by using the Z-score formula. The Z-score finding is 4.16. That is higher than Z-table (1.96) at 0.05 level of significance (4.16 > 1.96). It proved that there is a significant difference between the students who studied English and those who did not study English at elementary school. As shown by the mean score, standard deviation, and Z-score result, the students who studied English at elementary school improved their writing performance at junior high school.