In Finland, teachers' have extensive autonomy, that is freedom from control by others over their professional actions in the classroom, and it is considered a strength of Finnish education. At the same time, national assessment of learning outcomes has been constructed to examine the learner's progress and achievements in relation to the criteria of the Finnish National Core Curriculum for Basic Education in effect at the time. The national assessment of learning outcomes in music was conducted for the first time in 2011. In this article, the implementation and the main results of this National Assessment of Learning Outcomes in Music, in the ninth-grade of Finnish Basic Education are explored, and the whole process is examined critically from the perspective of teacher autonomy. The article discusses how, in the assessment, the ideals of teacher autonomy challenged assignment construction and the findings and conclusions of the national assessment. The article concludes that both teacher autonomy and national assessment are essential to compulsory education but must be balanced in a meaningful way.