Homeschool Grading Scale?

The following story might prove  one of several things:

1. I really am the meanest mom.

2. My son really is funny.

3. What I say is not always what my children hear.

In our homeschool, I don't really keep a record of grades until high school.  I do correct papers and give a score so I know if a subject is understood.  I teach for understanding in the younger grades.  I teach for understanding in the older grades, too, but by that time a poor score is usually a reflection of effort, not understanding (except math).

A couple years ago, when my youngest son was in the 9th grade, he confessed one day:

"I used to think our grading scale was-"

After I quit laughing, I thought:

Poor boy!  Is that really what he heard when we talked about doing your best?  

Is that what he heard when my husband talked about only making one 'B' his whole life?

Or were those just the words he put with the letters he heard his friends talk about?

What we say is not always what children hear.

My real grading scale is:

A = 90-100

B = 80-89

C = 70-79

Below 70 = Let's do that unit again because you obviously don't understand.

What is your grading scale?  What do your children think it is?

Have you ever said something that your children interpreted as something else?