The SchoolBook report and corresponding chart on the flow of students in and out of schools in Harlem, where there are more charter schools than any other New York City neighborhood, touched a nerve among those interested in the public school system.

Many comments focused on the question of unintentional versus intentional “dumping” of lower performing students from charters to the local zoned schools. Data from the Department of Education gave raw numbers of students leaving both district and charter schools over a three-year period. The numbers did not support charges of intentional dumping. The number of discharged students was not large and the discharges did not occur near testing season, as some charter critics have suggested.

Still, as reader Ruby Clinton said on Facebook, relatively low attrition rates at a Harlem charter school does not mean that zoned schools aren’t feeling the impact of charter schools in the neighborhood.

“NYC zoned schools could have higher attrition but still be ‘dumping grounds’ from charter schools. You’d have to analyze where students go when they leave, and the caliber of those students,” she said. “If low performing students are leaving charters and winding up at zoned schools, and there is no similar increase in high performing students, you will in fact wind up with a ‘dumping ground’ scenario.”

Education officials declined SchoolBook’s request to track where individual students went when they transferred out of a charter school, for privacy reasons. While the anecdotes about students who leave charters having lower test scores and behavior problems are legion, the data did not prove it.

However, charter leaders acknowledge that their strict behavior and promotion policies can be a turn-off to some families. Does that mean low-performing kids are more likely to leave charters? Possibly.

Parent activist Leonie Haimson answered absolutely yes in one Twitter comment.

“To receive 40 students is a lot; vast majority of students leaving charters are thought to be struggling,” she said.

On Twitter, charter school booster Campbell Brown called the report a “Must read. Important myth-busting about charter schools in NYC.” And Neeta Govind Vallab said the report “shows charter schools do not dump kids they deem unteachable. Let us not permit people to insert that fallacy into future discussions.”

Another issue debated on social media was the difference between turnover and attrition. Caroline Grannan said in a SchoolBook comment that “the press needs to make the distinction to avoid bolstering the misleading propaganda coming from the charter/’reform’ sector.” She continues:

“The attrition that’s criticized at ‘miracle’ charters such as KIPP schools means that many students leave (whether voluntarily or not) AND ARE NOT REPLACED. A study by SRI International of the San Francisco Bay Area KIPP schools, released in 2008, found that 60 percent of the students at the schools left AND WERE NOT REPLACED. The study also found that the students who left were consistently the less successful students.

KIPP and the entire charter/’reform’ sector have responded by misleadingly claiming that the same thing occurs at public schools. No, it does not. Again, students who leave public schools are replaced by incoming students (unless the district is experiencing an overall drop in enrollment). I did comparisons with high-poverty middle schools in the Bay Area, and their enrollment did not drop overall.”

One commenter applauded reporter Beth Fertig for taking the time to talk to parents. “The more we speak to PARENTS, the more we get to the truth. There are reasons why families line up and enter lotteries for charter schools,” she said.

Add your comments below. Check out the 10 charter schools with the highest attrition rates here. And stay tuned for more in our series on charter schools, coming later this month.