Then again - What is the success metric for education? Attendance is (IMHO) pretty terrible, and standardized testing hasn't worked out the best - so what is it?
A classic answer (but still, probably not all that great of one) is jobs upon graduation - but that doesn't help in elementary school.
So, how would you go about turning such long-term metrics as "employment in ten years" into short term metrics, to figure out what to do next week?
Success metrics are how you determine whether a change has worked, and they are how you determine where to put more resources. So if your success metric is attendance, you're going to maximize attendance, not quality of education.