In British Columbia, Canada, the school board did away with the D grade. Shortly thereafter, they formalized C- (C-minus) as an "official" grade. (The other pluses and minuses were not official). Effectively, they replaced D with C-. I've seen other schools which mandate that the lowest grade a student can earn in a quarter is 50%... that way, a student who doesn't answer a single test question or do any homework for a whole semester can still salvage his grade with new work in the third and fourth term, and pass. Alternately, once a senior has passes his first semester with a 75% or higher, gotten into his colleges of choice for the following year, there is no way he can fail the course for the year (75+75+50+50)/(4)=62.5, a passing grade.