[header] How to convince a teacher to let you retake a test [title] Decide what it is that caused you to fail the test. [step] Did you not study? Did you get in a fight with your parents? [substeps] Understanding why you failed can help you prepare for a retake. Think about how much of this information you're willing to share with your teacher. 
They may ask the reason for the retake, and you should be honest. If it's personal, you can make general allusions: " family problems, " or " a difficult personal period.