Recently, our friends on the left pulled a passage from a consultant report that found a statistical relationship between staffing levels and student performance. The consultants wrote,

We found that it was always true that high performing districts have more staff than low or moderate performing districts and that it is generally true that moderate performing districts have more staff than low performing districts. This pattern is true for teachers, school level administrative support staff and guidance counselors.

Does this mean that high performing districts are “high performing” because they have more staff? To put it another way, would low performing districts become high performing districts if the state simply added personnel? Of course not – correlation is not causation.