Thousands of kids are moving in and out of D.C. schools mid-year, according to an important study released today by the District’s Office of the State Superintendent of Education.

The report is the first of its kind in recent memory in the District, where there have been more rumors about student movement — especially between charter and traditional schools — than data.

My story in today’s newspaper touched on some of the questions the study raises. Here are some more that I couldn’t shoehorn into print, but are still worth noting:

Where are all those kids coming from, and where are they going?

More than 6,200 kids left charter and traditional schools during the 2011-12 school year. Another 4,600 kids entered city schools. During summer 2012, thousands more kids streamed in and out of the District.

No one knows for sure where those kids are coming from or where they go when they leave. They might have entered a private school or started home schooling; they also may have dropped out or moved to a school in Maryland or Virginia.

D.C. Public Schools Chancellor Kaya Henderson and D.C. Public Charter School Board Executive Director Scott Pearson both said we have to know more about these students, especially if we want to stem the dropout rate.

The numbers that the Office of the State Superintendent of Education compiled come from a citywide database of student information that shows enrollments in and withdrawals from D.C. public schools. The database doesn’t see beyond the District’s borders, nor into any private schools.

OSSE officials said they are pursuing data-sharing agreements with neighboring jurisdictions to better understand students who move across state lines.

Who is responsible for whether kids keep learning when they move mid-year?

A child who moves schools mid-year is often invisible, at least in terms of publicly reported standardized test results.

Every child who takes a test in the spring gets his individual scores back. But a student’s scores aren’t included in a school’s results unless that student has been enrolled for a full academic year — i.e., he was enrolled on Oct. 5 and was still enrolled in the same building when tests were administered in the spring.

A student who moves into the city mid-year from elsewhere will, similarly, not show up in the citywide results reported each summer, nor in sector-wide results for DCPS and charters.

It makes sense that schools shouldn’t be held accountable for kids they only taught for a few months. It’s also true that teachers — at least teachers I know — are motivated by far more than their kids’ standardized test results.

But in an educational world that increasingly relies on test scores to judge schools and teachers, the District’s mobility study raises questions about who is responsible for the achievement of mobile kids — especially those kids who switch schools most frequently, and might be among the neediest kids in their classroom.

When are students most likely to leave schools?

OSSE officials say they are confident in the overall picture of mobility that their study presents, but they caution that the monthly entrance/exit figures should be taken with a grain of salt.

That’s because changes show up when they were recorded by schools in the computer system, not when they happened in real life. So a student may have withdrawn in November, but that exit might not show up in OSSE’s report until January because of a record-keeping delay.

That quirk may be especially important in interpreting charter school exits.

Charters show a bump in exits in March and April, a fact that critics might say proves that they are “dumping” kids before standardized tests in the spring.

Pearson said he’s seen no evidence of that. He took the helm in January 2012 and soon thereafter, his new staff began a concerted push to get schools to clean up their enrollment books. The spring bump is an artifact of that push, he said, but many of the students had actually withdrawn from their schools earlier in the year.

Pearson also pointed out that the data shows that charters accepted more than 1,500 students during the school year. That contradicts popular wisdom, he said, which holds that charters refuse to take new kids after Oct. 5 — after which charters’ funding levels are locked in no matter how many students they gain or lose.