By Adam Pagnucco.
In Part One, we reviewed County Executive Marc Elrich’s critique of MCPS’s measurement of class size. In Part Two, we listed the kinds of class size estimates that MCPS has published over the years. Today, let’s dig into the data.
Let’s start with three measurements of class size in elementary schools: kindergarten, grades 1-3 and grades 4-5. The first measure has been published almost continuously since FY03 while the others have been published almost continuously since FY06. The chart below shows all three up through FY24.
Three oddities can be immediately seen. First, none of the three measures were published in 2010, when MCPS was in the midst of the Great Recession. Second, there was a dip in kindergarten class size and spikes in the other two measures in 2013 and 2016. No explanation was given for the 2010 omission or the two years of dips and spikes. The definition of average class size in elementary schools in 2013 and 2016 is identical to the definition used today.
There do appear to be slight dips in elementary school class size during the pandemic, which would make sense given that that is when MCPS’s enrollment started to shrink. But due to questions about the historical data in this series, I’m reluctant to firmly draw that conclusion.
Now let’s look at English and other course class sizes in middle schools. Both series have been published since FY03 with no changes in their definitions.
Once again, we encounter an oddity. Average English class size dropped from 24.5 in 2017 to 16.0 in 2018. Average other class size also dropped from 25.1 in 2017 to 16.6 in 2018. The definition of class size in secondary schools did not change from 2017 to 2018 despite the vast differences in calculations.
We see the same issue in English and other class sizes in high schools as shown in the chart below.
Average English class size dropped from 24.5 in 2017 to 16.3 in 2019. Average other class size also dropped from 25.6 in 2017 to 16.2 in 2019. Once again, the definition of class size in secondary schools did not change from 2017 to 2019.
Note that these dates (2017 through 2019) precede the pandemic so it can’t blamed for that pattern.
Another stat seen in the middle school and high school series is large increases in class size starting in FY24. Is that due to students returning to MCPS after the pandemic? That’s unlikely since the historic enrollment statistics shown in the superintendent’s recommended capital budget show that the district has been experiencing an uneven drop in enrollment starting in FY20.
So is any of this real? Honestly, who knows? I am skeptical of any measure that claims average class size over a system as vast as MCPS can vary by 30%, 40% or more in a year or two. I might give it more credit if it was accompanied by a clear change in definition of class size, but I don’t know of any such explanation.
I asked MCPS for an explanation of how they calculate class size on January 6. As of this writing, I have not received a response.
As a result, I am very skeptical of any claims that MCPS makes regarding class size until the above statistical issues are resolved and explained.
That said, there are a few other stats that may have more explanatory power. We will explore them next.