This has to be the dumbest policy to come along in a while. Besides a fundamental misunderstanding of how grades are assigned (hint: its not a random number between 0 and 100), it minimizes a teacher's input and leeway into how to grade students.

When I was a TA, granted these were college students, the only reason you received a zero on a grade was because you didn't take the test, turn in an assignment, or do a project. If there were extenuating circumstances, like illness, you could take the test at a later date, or the teacher could decide to drop that exam altogether from your grade and re-weight the other exams in the course. All this minimum 50 policy does is give students another way to game the system. If you know you're going to fail, or not complete an assignment, who cares? It won't hurt your grade as much as getting a zero!

At some schools, failure goes from zero to 50 - USATODAY.com

"It's a classic mathematical dilemma: that the students have a six times greater chance of getting an F," says Douglas Reeves, founder of The Leadership and Learning Center, a Colorado-based educational think tank who has written on the topic. "The statistical tweak of saying the F is now 50 instead of zero is a tiny part of how we can have better grading practices to encourage student performance."