This isn't directly MY success, but was a very neat thing to see.
I took on the task of a home-bound instructor for an ill student. During my first visit, we had some math to do. We worked through a concept review activity which would help formatively assess where she was to see if she was ready to move forward or to get more instruction. As part of this activity, the math teacher had written the concept goals as well as which questions would tell the teacher and student the level of understanding. After the student was done, we looked it over together and had decided that she understood the Level 2 questions perfectly, but was struggling on a few specific parts of the Level 3 things. Those struggles made approaching the Level 4 question quite challenging.
Today, I went to school and chatted with the math teacher. I told her I was going to "test" her, the teacher, on the 4-Level rubric with this student. I told her just what I said above, solid on Level 2, struggling but almost there on Level 3. She replies, "Well, she must be able to set up the ratios and proportions using whole numbers, but must be having troubles when the scaling factors have decimals."
HOLY COW! Exactly right.
In the end, the goal of grading is to communicate. This teacher has set up a system that works. Clear goals matched with quality assessment. Awesome. As an "in-between" teacher in this case, the system worked nicely too as I could easily give the student some specific practice that will allow her to make that tiny step to be at a Level 3.