The present work empirically examines the validity of Student Self-Assessment (SSA) as an educational assessment in higher education. We briefly review the principle methodological factors that could affect SSA validity, as well as the main findings identified in the literature. One empirical study is presented that compares student-self evaluations on a test with the evaluation made by the course instructor while controlling for students' experience with SSA, criteria, rubric, and scales used by the student and teacher, and that the teacher was blind. Results show a strong correlation overall between the SSA and the instructor's evaluation and show that lower-performing students tend to over-estimate their performance while higher-performing students under-estimate their performance. The results support that SSA is valid for the average student, but less so for those that deviate above and below average in the absence of measurements of potentially mediating variables. The need to consider metacognitive factors in SSA is proposed.