Abstract :
SMA N 1 Air Kumbang is a school that has computerized data storage, one of which is student majors data. The majors for SMA N 1 Air Kumbang students are carried out at the beginning of the school year in accordance with the 2013 curriculum which has 2 majors, namely Natural Sciences and Social Sciences, which aims to channel the abilities and interests of these students. In determining student majors, so far the process of classifying majors has not been implemented and the accuracy is also unknown. This study aims to classify student majors and apply data mining methods using the C4.5 decision tree algorithm and also the Rapidminner application. This classification uses 6 attributes as control attributes which are the average grades of junior high school report cards which include subjects B. Indonesian, B. English, Mathematics and Science, as well as recommendations for junior high school counseling teachers. Based on tests carried out on students in the 2022/2023 school year with a data sample of ± 400 data with the attributes of the recommendations of Middle School Guidance and Guidance teachers that influence student major decisions. The results obtained were an accuracy of 84.27% and a classification error of 15.73%. From the results of the accuracy of 84.27% is in the range of 0.80-0.90 and these results are included in the Good Classification category. Thus it can be concluded that determining majors using data mining decision tree algorithm C4.5 can speed up and accurately make major decisions for SMA N 1 Air Kumbang students. Keyword : Datamining, Classification, Decision Tree, Algorithm C4.5