This study aims to test the effectiveness of Self-Assessment Based Counseling services using Quasi-Experimental Pretest-Posttest Nonequivalent Group Designs. Research subjects totaled 105 high-school students consisting of 53 male students and 52 female students. Subjects were divided into two groups, 55 students in the experimental group, and 50 students in the control group. The research data on the form of a certainty score of students' further study plan was measured using the Certainty Scale of Further Study Plan. The results indicate that self-assessment counseling services are effective to help high school students improve their further study plan certainty. The average score of students from the experimental group increased significantly compared to students from the control group. The scores of male and female students did not differ significantly, and their mean scores showed equal improvement. The use of self-assessment in further study counseling does not depend on the sex of the students, both for men and women equally effectively.