A few updated NJ charter figures

Posted on November 10, 2010

New, updated slides in PPT format (for clarity on labels): CHARTER SCHOOLS_NOV2010

I expect people will be asking why some of my figures previously posted don’t match up exactly with figures presented by others on New Jersey Charter Schools – including those produced by ACNJ in a new report.  In short, the answer is that at least with regard to “poverty” measurement and comparisons across charters and Newark Public Schools, they are different measures. In my previous slides I show a bar graph of Free Lunch rates and later show scatterplots of performance by Free or Reduced Price Lunch rates. ACNJ and many others use only Free or Reduced lunch rates, never exploring the distinction between the two. Seems like a subtle difference for the lay reader and one that might not sink in right away. But, it can actually be an important distinction in this type of comparison.

Here’s a link to the differences in eligibility guidelines: http://www.fns.usda.gov/cnd/governance/notices/iegs/iegs.htm

For children to qualify for Free Lunch, their family income levels must be below the 130% income level with respect to the Poverty Income Level (30% above poverty line). That is, kids in families who qualify for free lunch are in families up to that level.

The income threshold for Reduced Price Lunch is the 185% income level with respect to the poverty income level.

The fact is that most school aged children in Newark fall under the 185% income level with respect to the poverty income level. As such, most schools in Newark have over 80% children in this category. Therefore, it is hard to use this relatively “generous” income threshold in order to distinguish differences in populations across Newark Schools- NPS or charter. The lower income threshold serves as a better way to distinguish the differences.

Here is the % Free Lunch using NJDOE 2009-10 data: http://www.state.nj.us/education/data/enr/enr10/

These data are highly consistent (except for Lady Liberty) with my 2008-09 data from the National Center for Education Statistics Common Core of Data. Most Newark Charter Schools, especially the frequently touted high performers, have very low relative rates of children below the 130% poverty threshold.

Here is the % Free or Reduced Lunch using NJDOE 2009-10 data:

Here, the charter schools scatter themselves more widely among the NPS schools. They appear more comparable and their average is only marginally different by some accounts. BUT, the reality is that most kids in Newark fall under this threshold and nearly every school in the above figure exceeds 70% free or  reduced lunch and the vast majority exceed 80%. This higher income threshold limits our ability to distinguish real differences in student populations across Newark schools.

Another angle would be to say that the difference in the position of charter schools in the second graph versus the first is an indication that CHARTERS ARE SERVING THE LESS POOR AMONG THE POOR.  Not all, but many are doing this. Most surprising perhaps is that Robert Treat in particular remains a standout even with regard to the less poor.

Additional Figures:

Here are the special education classification rate data for 2004 through 2007:

NJDOE has not posted the more recent classification rate data by the same format. Enrollment files used in the first part of this post have disaggregated classification data, but report mostly “0” values for charters because counts were too small to report. NJDOE does report placement data, but again, these data are spotty at best for NJ Charter schools.

Here are the frequency distributions by school, for Newark Schools, by Free Lunch and by Free or Reduced Lunch. As you can see, the distribution for Free or Reduced Lunch is all crunched in the range above 80% making it more difficult to distinguish true poverty differences among schools serving Newark children.


  1. When comparing across schools within poor urban setting, compare on basis of free lunch, not free or reduced, so as to pick up variation across schools. Reduced lunch income threshold too high to pick up variation.
  2. When comparing free lunch rates across schools either a) compare against individual schools and nearest schools, OR compare against district averages by GRADE LEVEL. Subsidized lunch rates decline in higher grade levels (for many reasons, to be discussed later). Most charter schools serve elementary and/or middle grades. As such they should be compared to traditional public schools of the same grade level. High school students bring district averages down.
  3. When comparing test score outcomes using NJ report card data, be sure to compare General Test Takers, not Total Test Takes. Total Test Takers include scores/pass rates for children with disabilities. But, as we have seen time and time again, in charts above, Charters tend not to serve these students. Therefore, it is best to exclude scores of these students from both the Charter Schools and Traditional Public Schools.

ACNJ’s Newark Kids Count 2010 report appears to fail on all 3 guidelines above.

ACNJ’s Newark Kids Count: http://acnj.org/admin.asp?uri=2081&action=15&di=1841&ext=pdf&view=yes


One question raised by the ACNJ Kids Count yearbook is why the NPS schools hold ground with Newark Charters through 4th grade, but appear to lose ground in 8th grade. The charter advocate explanation is that charters are simply doing better, cumulatively, with students through 8th grade and preparing them for college. However, there are two other equally if not more likely explanations.

First, the mix of schools that are charter schools serving 8th grade students is different from the mix serving 4th grade students. Heavy “cream-skimmers” like North Star Academy start at 5th grade. And some lower performing charters, actually serving more representative populations end at 4th grade. The different mix of charters having students taking the 8th grade test versus those taking the 4th grade test may explain a substantial portion of the difference. It’s also important to understand that at this break – where low performers end – and where high performers start up – that many low performing students may be pushed back into NPS schools and meanwhile, higher performing ones creamed off.  Here are the charter school proficiency rates (general test takers only) from 2009 state report cards, along side NPS proficiency rates (averaged across tests).

Second, charter schools have the ability to use cohort attrition to their advantage, over time, shedding the students who perform less well on assessments, perhaps due to the extent of parental obligation involved in keeping students in the school or even due to the message that the child “just can’t cut it here.” NJDOE data don’t allow for precise student level tracking to see whether individual students stay on in particular charter schools or which students do. But, one can do a relatively simple back of the napkin approach using the grade level enrollment files to determine whether or not cohort attrition may be an issue. Note from the performance graph above, North Star in particular shows incrementally higher proficiency rates at each higher grade level. While this is not a cohort comparison, it is possible that this pattern arises due to attrition of weaker students in higher grades.

Here’s a quick look at 3 cohorts of 5th graders across these schools:

This tabulation shows significant cohort attrition for North Star in particular.

Now, there is nothing particularly conclusive about the above slides, but they do raise questions as to whether the difference in 8th grade scores between NPS and Newark Charters is at least partly if not substantially a function of a) the different mix of schools serving 8th grade and b) the significant cohort attrition of at least one of the larger schools. Note that these attrition patters, if shedding lower performing students have the effect of both raising the charter 8th grade average and depressing the NPS 8th grade average.