Whoa! That's the toughest scale I've ever seen. 69 an F? That's sometimes a C+ depending on the prof and curve
He even skips a D.
First of all, 20% of the grade is homework. Every assignment must be in an Excel file, which I critique and return within 48 hours for corrections. Any student can earn 100% on this part of their grade. And I give a 20 minute quiz every week (6 times) on the current assignment, worth 1 point of EXTRA credit, bottom line.
Then, I use a variable grading system on both the midterm and the final tests, but the tests are pretty tough. Both tests are open book, open notes and corrected homework, and free use of any calculator you like, including a computer.
I determine the class average for each question, then assign higher weights to questions with higher averages and reduced weight for lower ones, to compensate for the question difficulty and the effectiveness of my teaching. Then I look for very high and very low grade "clusters", to determine if I need to remove these students from the distribution. Finally, I assign the 70-99 range, and reassign any grades that were outside of it.
Out of 37 students, I have given 4 C grades and no F's, but I have had a LOT of dropouts. This is a tough course - perhaps the toughest in the MBA cirriculum. But my last class earned 4 A, 2 A-, 1 B+, 1 B, 2 B-, and a C. And I have 13 unsolicited Emails from former students that either tell me they use or expect to use what they learned in my class, or just that the class was a positive experience for them.