I hate to give kids failing grades on quizzes, tests or labs because the impact on their overall grades is so dramatic. However, sometimes it's the only thing that gets them moving or gets the attention of busy parents. I have a several students who failed a quarter or came close to it. With diligence, and in some cases, tutoring, they are now making 100% on assessments. Most of them have the ability, but they've been permitted to slide through with minimal effort throughout their academic careers.
70 is passing? Do you not have the equivalent of a D grade?