Step 1
The average “margin of error” of a New York City teacher was plus or minus 28 points.
Step 2
The value-added scores can often change between years.
Step 3
The value-added scores can often change between years (Ravitch, 270).
Step 4
According to Ravitch, performance ratings are hard to trust (Ravitch, 270).
Step 5
According to Ravitch, value added scores “fluctuate between years” (Ravitch, 270).
You clearly understand the essential concept, but forgot to cite the full source at the bottom of the exercise.