Fred Smith is a testing expert who knows how test scores can be manipulated and statistics can be twisted into data pretzels.

In this post, he calls out Mayor de Blasio for hyping the numbers to make the gains far larger than they were. Leave aside for the moment that test scores are a ridiculous way to measure the quality of education. Leave aside the fact that using them as measures of progress feeds into the privatizers’ narrative. Smith caught the Mayor juking the stats for Political gain.

He writes:

Ignore that tall man behind the curtain as he cranks up the volume.

Bearing a strong resemblance to Mayor de Blasio, he is there to proclaim that, “Since 2013, English proficiency has increased by 54 percent and math proficiency has increased by 27 percent.” But the noise machine can’t hide the fact that there is little substance in all the thunder.

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So, the mayor’s Tuesday press release leads with huge gains in reading and math scores—the major, if-you-don’t-remember-anything-else point he wants us to take away as he seeks re-election.

But the percentage gains are statistical smoke that befogs the mayor’s already clouded efforts in education. And, frankly, they raise questions about the incumbent’s honesty.

Three tricks prop up the testing headline:

1. The DOE press release emphasizes percentage gains, which are current results minus previous results divided by previous results. Evidently, the increase in English scores of 14.2 percent (26.4 percent to 40.6 percent) from 2013 to 2017 wasn’t good enough news. Nor was the 8.1 percent gain (29.6 percent to 37.8 percent) in math. So, the press office reaches into its bag of tricks and insists there has been a 54 percent gain in English proficiency under de Blasio—14.2 divided by 26.4 and a 27 percent boost in math—8.1 over 29.6.

Now, can you imagine the mayor doing this if there had been an increase in the murder rate. Let’s say homicides were up from 6 to 7 killings per 100,000 New Yorkers. Would de Blasio say that murders rose by one percent or by 16.7 percent? You know he would minimize the negative outcome.

2. – De Blasio’s spinners also present 2013 as their baseline year. But Mayor Bloomberg owned the 2013 results and most of 2014’s, as well. De Blasio didn’t arrive at City Hall until January 1, 2014. The English test was given on April 1, 2014.

Why would they go back to 2013? It allows de Blasio to start his story the year the ELA and math results tanked–creating a fictional narrative of tremendous achievement. For 2013 was the year the Common Core-aligned tests descended on the schools and rained rigor down on 440,000 New York City students. De Blasio wants to embrace Bloomberg’s bottomed-out, third-term school years as his starting point, because things could only improve after that.

Had the Mayor begun his account with the 2015 results, he would still have a 10.2 percent increase to boast about in English proficiency (from 30.4 percent to 40 percent6 percent), but only a 2.6 percent gain to show in math (35.2 percent to 37.8 percent) under his control of the schools. That would be nothing to brag about.

Ironically, as he notes, Joel Klein too tried to claim credit for test score increases that occurred before he took office.

Sad that test scores are now a political talking point. Just proves how meaningless they are.