Look - if a good student has a bad day and gets a C (75%), but previously had an A (95%), their grades average to a B (85%). It's nicely and evenly in the middle.
A student who's having a rough time who gets a low F (say 20%) but previously had a middle C (75%) will have an average of an F (47%).
A student who starts with a B average (85%) and gets a low F (20%) ends up with an F (52%).
A student who starts with an A average (95%) and gets a low F (20%) ends up with an F (57%)
A low F brings an aggregate grade down by far, far more than any other grade can affect it. This isn't really up for debate - this is how the math works.
Do you think it's reasonable that a badly flubbed test can bring an otherwise good student's grade all the way down to an F? Remember, this isn't solely about missed assignments.
Let's try different tack. Scrap percentages.
- Would you support a grade system in which A is worth 4 points, B is worth 3 points, C is worth 2 points, D is worth 1 point, and F is worth 0 points?
- Would you support a grade system in which A is worth 9 points, B is worth 8 points, C is worth 7 points, D is worth 6 points, and F is worth 0 points?