Charter school graduation data

I'm starting to feel like a broken record, but I feel like this article explains something I hadn't understood before and which might be helpful to those wishing to understand why charter school data is skewed and thus impossible to compare with data from traditional public schools.

In some cases, charter schools are able to have higher graduation rates than neighborhood high schools (i.e. regular public schools) because they can transfer out students at will, whereas the neighborhood school is a "school of right" which guarantees education to every child who lives within their boundary district.

For example, if a charter has 50 10th-grade students on their books, but only 30 who look like they might meet graduation requirements on time, they can transfer out those 20 problematic students at the end of 10th grade. If the rest succeed as expected, the charter school will have a 100% graduation rate two years later.

When a charter transfers students out of their school, those students must enroll at another school in order to shift out of the charter school's cohort (i.e. so that they do not read as a student of that charter school who failed to graduate). Many re-enroll at their local neighborhood high school. However, if a student drops out of a neighborhood high school and does not re-enroll elsewhere, that student remains on the books of the neighborhood high school as a non-graduating student. Charters will never, ever have this particular issue because they can push out students at will. Neighborhood high schools have nowhere else to dump students.

One remaining question I have is: is the onus at all on the charter school to ensure that a student is re-enrolled elsewhere, or when they are removed from the charter school, are they automatically added back to the local neighborhood school's cohort?

This was brought to my attention by an excellent analysis by Erich Martel, a retired DCPS social studies teacher who unrelentingly excoriates the neoliberal education reform sweeping Washington, D.C.
"Don’t students drop out of the regular public school?  Certainly.  When they drop out, they are still counted in the school’s cohort (denominator).  A student can only be removed from the denominator/ cohort, if he or she is transferred to another school and enrolled. The regular public school has no equivalent “default” LEA into which it can unload unwanted students.  Since charters are all in the same school zone as the regular public school, they can transfer at will.
After a student has been transferred to the LEA school of right, i.e. the “traditional” public school, he or she is removed from the cohort.  The US Department of Education introduced the Adjusted Cohort Graduation Rate (ACJR) calculation with the graduating class of 2011.  It starts with the grade 9 enrollment, students transferring in are added; those transferring out are subtracted from the cohort.
When there are multiple LEAs in the same geographical district, but only one is required to enroll all students, the other LEAs have the privilege of cherry picking and then getting rid of students who don’t fit in.  That’s what they all do in DC, including much acclaimed KIPP."
As posted on GF Bradenburg's blog, here:

http://gfbrandenburg.wordpress.com/2012/11/06/from-one-washington-to-the-other/