Earlier this week Education Commissioner Christopher Cerf urged caution in regards to news that cost per pupil in our poorest districts was lower than last year according to the newly-released 2010 New Jersey School Report Cards. “The data are not completely accurate,” he told the Star-Ledger. “These data need to improve.”

Old news. Griping about the NJ Department of Education’s ability to manage data is a popular sport, including right here. And fair game too: one of the reasons we lost Race To The Top was a low score on “Data Systems.” Out of a potential 47 points we got 27. Out of 41 states that applied, only 8 scored lower than us.

So I was trolling the state data base for the annual description of two Burlington County towns nine miles apart in distance and light years apart in achievement: Moorestown and Willingboro. Nothing new, sad to say, at least if you’re a family in Willingboro. Moorestown High, for example, boast stellar HSPA (High School Proficiency Assessment) scores, which is the qualifying test for graduation. Almost all kids passed it in 2010 (5% failed in language arts and 9.5% failed in math) and, in a salient indicator of success, 98.2% of high school seniors graduated through successful completion of the HSPA. (Kids with significant disabilities can substitute a sort of portfolio review. Students who fail the HSPA three times can take the AHSA, though that’s another story.)

On down the road to Willingboro High. Test scores for 2010 are grim. 41% of aspiring high school graduates failed the language arts portion of the HSPA. A stunning 75.1% failed the math portion.

But here’s where it gets confusing: according to the state data base, 87.4% of those aspiring seniors graduated by passing the HSPA.

Question: how can 75% of the class fail the test but 87% pass the test?

It’s not exactly a trend in Willingboro. According to the historical data, in 2009 41.7% of Willingboro High’s students failed the language arts portion of the HSPA and 63.3% failed the math portion. 55.2% of students graduated by passing the HSPA, which seems far more proportionate than this year’s 87%.

A little more snooping around reveals that most struggling districts’ numbers make sense. At Camden City High 80.7% of students failed the language arts portion of the HSPA. (The math portion is left blank because so many students failed that disclosure might risk student identification.) According to the Report Card, 21.2% of students graduated by passing the HSPA. Another example: at Plainfield High, 43.5% failed the language arts portion, 66.2% failed the math, and 57.6% graduated via the HSPA. Similar logic prevails in Paterson, Pleasantville, Newark, East Orange.

But Trenton Central High’s number are wonky too. According to the just-released data, 39.8% of high school students failed the language arts portion of the HSPA and 71.5% failed the math portion. Yet 91.9% of students graduated by successfully completing the HSPA exams.

Any ideas on how to reconcile these numbers? Maybe it’s just a missed key stroke. Or maybe diplomas were awarded based on this data. Anyway, please jump right in.