Last week I wrote that Arizona's open enrollment policy is one of the three major factors leading to the decline in TUSD enrollment since 2000, the others being charters schools and a slowdown in Tucson's population growth. I estimated somewhere between 1,500 and 3,000 students living inside district boundaries attend schools in other districts.

It looks like I low-balled my estimate. The actual figure appears to be at least double what I came up with, meaning the impact of open enrollment on TUSD's loss of students, and on Arizona's education landscape, is more significant than I realized.

Since Arizona's new open enrollment policy was put into operation in 1995, students can attend any public school that has an empty desk. In district, out of district, it doesn't matter so long as parents can find a way to transport their children to the schoolhouse door. Students inside a school's attendance area and inside the district get first shot at going to a school, but after that, it's open to everyone.

So how many students living in the TUSD attendance area go to schools in other districts? In my post I arrived at a range of students by the back door. I looked at the number of open enrollment students in the Catalina Foothills School District — a whopping 3,000 out of a total student population of 5,200 — along with anecdotal information from Vail School District and used that to arrive at an estimate of 1,500 to 3,000 students. I was pretty sure that was low, but I wanted to stay on the conservative side.

A few days after I finished the post, by one of those odd coincidences which happen all the time, an Arizona Charter Schools Association piece came across my desktop with figures about how many students participate in open enrollment. In the study it cited, 31 percent of students in 9 Maricopa County school districts went to public, non-charter schools which weren't their neighborhood schools. That's twice the 16 percent who attend charter schools.

It's important to note that the Arizona Charter Schools Association, a nonprofit organization which gets $1.5 million a year from the Walton Foundation (I try to include that bit of information whenever I write about the group), is a cheerleader for all things "school choice," so I should question any numbers it promotes which make "choice" look good. But the figures are drawn from what looks like a careful academic study, and the charter school figures are in keeping with state records, so I'll accept the 31 percent open enrollment figure as reasonable.

By contrast, my estimate of TUSD-area students who take advantage of open enrollment to attend out-of-district schools was between 2 and 6 percent. The 31 percent figure from Maricopa makes me think my estimate was much too low.

The problem with the study's data for what I've been working on is, it includes all students who attend schools outside their neighborhoods, including schools inside and outside the students' districts. How many attend schools outside their own districts? The study doesn't say.

So once again, I'm on my own in figuring out, first, if TUSD also has 31 percent of students in its boundaries attending schools outside their neighborhood, and second, how many of those leave the district. Time for more educated guesswork.

TUSD likely has a similar number of open enrollment students in its attendance area as the Maricopa districts in the study. Because of our city's dense population, our schools, like those in the Phoenix area, are close enough to each other for parents to have a wide variety of choices within a reasonable distance. So I think a figure close to 31 percent figure makes sense for TUSD.

I'm going to estimate a third of open enrollment students leave TUSD for another district. The two most attractive districts from a standpoint of test scores, Catalina Foothills and Vail, are right next door, so it would be a reasonably short drive for parents to ferry their children to either districts, and there are a number of other districts close by. The only limit, really, would be the number of seats available in each district.

That would give me a ballpark figure of 6,000 TUSD-area students whose parents take them to schools in neighboring districts.

In my earlier post, I estimated 9,500 TUSD-area students attend charter schools. That's in keeping with statewide percentages, so it's close to correct. Add 6,000 using open enrollment to attend out-of-district schools, and you get a total of 15,500 students. That's close to the 16,500 drop in TUSD enrollment since 2000. Even if my estimate is off by a few thousand, open enrollment and charter school students account for most of TUSD's enrollment loss.

Remember, those 15,500 students are able to leave their neighborhood schools because of laws enacted in 1995 creating charter schools and open enrollment. So if you're looking for the primary cause of TUSD's precipitous drop in enrollment over the past two decades, turn your gaze away from the district's administration, teachers and curriculum and look to the Republican-majority legislature in Phoenix and the privatization/"education reform" movement it embraced.