What can I do to avoid the yell?

Be straightforward, and before they even get a chance to speak (or yell), tell them everything. That includes explaining why the bad grade happened and how you will improve. Often the reason they will yell is for lying, or if you refuse to keep trying and say that you can't get better. That really upsets parents because they'd rather see you meeting the challenge than avoiding it. If you are scared of your parents and they yell at you for everything, this might be a case of verbal abuse and you may find it helpful to read [[Deal With Emotional Abuse from Your Parents (for Adolescents)|How to Deal With Emotional Abuse from Your Parents (for Adolescents)]].