What makes anyone think that a graduation rate of 67% should be the magic point at which a high school should be "singled out"? 
Why not 97%? 
Or 87%?
Or 77%?
After all we are already grading on a curve.

Why rate an individual high school at all?  Why not the whole district in every case?
Any district is only as good as its worst performing school.

Are "alternative high schools" just a a way to isolate poor stats as well as struggling students?
Are they not primarily intended as a way of making the district's "regular" high schools look better?