I've also be clear that I believe the reason the test scores are higher is that not only are classrooms sizes small
etc. etc. but that AF and other charters are pulling those students that are less
poor, speak primarily English, do not go home to households that don't have English as their primary
language and have fewer special education needs.
However, students are not randomly assigned to teachers — and statistical models can not fully adjust for the fact that some teachers will have a disproportionate number of students who have greater challenges (students with
poor attendance, who are homeless, who have severe problems at home,
etc.) and those whose scores on traditional tests may not accurately reflect their learning (e.g. those who have special education needs or who are new English
language learners).