The objective of this research is to evaluate the validity and effectiveness of assessing the competencies of 10th and 12th grade students at SMAN 7 Yogyakarta in the Indonesian language using assessment instruments such as essays, multiple-choice questions, and quizzes. The study subjects were Indonesian language teachers at SMAN 7, Yogyakarta. The research utilized qualitative data. The results indicated that the use of assessment instruments in the Indonesian language subject on students' competencies is valid and effective, depending on each student's abilities, as not all students possess the same level of competency. Several factors must be considered for students, including the use of appropriate assessment instruments. According to the informants, this involves a system in which students provide feedback to one another. Students' work should not only be evaluated based on academic grades, but also on their attitudes. The assessment instruments at SMAN 7 Yogyakarta are currently providing efficient evaluations. In addition to essays, multiple-choice, and quiz instruments, other instruments used include books, pictures, video playback, and adapting the given subject matter. The assessment process involves enrichment for students who meet the minimum competency criteria and remedial measures for those who do not. The last factor influencing assessment is not only the students' ability to answer questions or solve problems, but also the neatness of their writing.