If there’s one statistic that supporters of lifting the cap on charter schools in Massachusetts cite more than any other, it’s this one: 

“Because of an outdated and arbitrary cap on the number of public charter schools, almost 33,000 children are stuck on waiting lists” for charter schools.

The quote comes from the website of Great Schools Massachusetts, a group that has raised more than $18 million toward supporting Question 2 on this November’s ballot, which would lift the cap on Massachusetts charter schools. It’s a point that’s been emphasized by supporters of lifting the cap in debates, TV ads, public testimony and newspaper editorials. 

But data from the state’s Department of Elementary and Secondary Education analyzed by WGBH News would seem to cast doubt on every part of that assertion: While many students appearing on those lists may indeed be “stuck” in schools of lesser preference, charter school wait list numbers provide little, if any reliable indication of how many.

When students and their parents apply to charter schools, they may, and often do, apply to more than one; and they may end up on wait lists for several at once.

The state’s Department of Elementary and Secondary Education does attempt to provide the number of “unique” students on wait lists, rather than a larger count including students applying to multiple schools. Before DESE began using that number, a year ago, the wait list number appeared to be over 50,000.

But there is no way to tell whether students appearing on one charter school’s wait list have already enrolled, perhaps happily, at another school—including another charter or district school.

A spokesperson for DESE confirmed that students’ names remain on charter school wait lists unless a parent specifically requests the student be removed from the list, or until the lists are “refreshed,” later in the year. DESE does not itself remove students from wait lists even if they’ve enrolled in another school.

The 33,000 figure also includes close to 10,000 students who applied for admittance in prior years, effectively assuming that they are still “waiting” for placements even if the students haven’t re-applied.

This practice of “rolling over” names, and the state’s allowing it, were criticized in a 2014 State Auditor’s report on DESE’s data collection practices for charter school wait lists, which called on DESE to “fully prohibit the use of rolling wait lists.”

Instead, the department issued guidelines suggesting that charter schools only count new applications, but giving them the option not to. Eleven charter schools chose not to take that advice, reporting 9,700 students as “waiting” for seats they hadn’t applied for that year. 

Counting only students who were placed on wait lists this year, the number drops to just under 23,000—or 33 percent less.

WGBH News found that more than 9,000 students are on wait lists for seats in grades for which charter schools are not required to “backfill” seats even as they become vacant.

Most students, not surprisingly, appear on wait lists for grades representing the first grade level offered by a given charter school—usually, though not always, kindergarten or pre-K.

But while district public schools are required, under most circumstances, to take new students as seats become available, Commonwealth charter schools are exempt, under state law, from filling vacancies in the middle of the school year and for grades 10 to 12 or the uppermost half of all grades offered—as many as five grades in some charter schools. 

How many of the (roughly) 9,000 students wait-listed for seats in later grades that charter schools don't have to fill are waiting because of a lack of charter schools—or because charter schools may opt not to take them, even if they have vacancies—isn't clear.

Of the 23,000 students who appeared on wait lists that weren’t rolled over from previous years, more than 3,600 also appeared on wait lists for so-called “Horace Mann” charter schools—district-run charter schools in Boston, which would be unaffected by Question 2, which raises the cap on “Commonwealth” charter schools (this category includes all charter schools in Massachusetts with the exception of Horace Mann schools).

Boston Public Schools, meanwhile, has a standing wait list of 6,981 students looking to change schools within the district, according to figures supplied by BPS—a number which doesn’t include the 3,646 students waiting for BPS-operated Horace Mann charter schools.

How many students waiting for charter schools are also on wait lists for Boston Public Schools—or vice versa—is not clear.

Great Schools Massachusetts, a nonprofit group pushing for the passage of Question 2 on this November’s ballot, referred questions regarding the wait list numbers to state officials and did not offer its own response to questions by WGBH News over the accuracy or portrayal of charter school wait list numbers cited in advertisements and on its website.

Lisa Guisbond, executive director of Citizens For Public Schools, a nonprofit which opposes Question 2 and the expansion of charter schools in Massachusetts generally, says that the DESE publishing the problematic 33,000 figure for students on charter school wait lists is irresponsible and plays to the pro-expansion side of the charter school debate.

There is demand for charter schools, Guisbond concedes. But “we don’t know what it is. And when you look at the data they actually have, it’s not close,” to the 33,000 figure oft-cited by proponents of expansion, Guisbond said.

“There are waiting lists for Boston district schools as well,” Guisbond said, adding that another 14,000 children are on wait lists for state-subsidized pre-school.

“So why do we keep focusing on one waiting list to the exclusion of the other waiting lists?” she asked.

Waiting lists for the Boston Public Schools represent students moving within the district, rather than contemplating leaving it.