@maxdancona,
That is very similar to how my ddaughter's school approaches this. The school system determines the overall grading parameters .... A-F system and/or number as in a GPA (which they all so use in high school). But the teacher derives how the students obtain those grades. Most teachers like you state hand out precisely how they grade so you know from the start.
There are many teachers though who are flexible with their grades where if the math calculates you on the cusp they may boost you to the next level ...say you are a kid who is always in class, participates and seeks extra help, etc. .... or drops you ..if you are a kid who is not engaged, disrupts.