Assuming the teacher is half-decent and student isn't "witless" (or R-word; no offence to anyone but that word perfectly captures the meaning), then the blame is on the student. But what kind of test are you talking about here? Simple school quizzes/unit tests don't matter. College-entrance exams, most school teachers are not good enough. Tuition/coaching teachers quality would depend on location, batches, class strength etc. University exams i have no idea.If a student fails an exam/test, does the blame lie on the teacher or the student?