The highest-achieving students are doing better and the lowest are doing worse than a decade ago. That’s one depressing revelation from the latest Nation’s Report Card that details how America’s union-run public schools are flunking.

The results from the 2019 National Assessment of Educational Progress, which is administered to students around the country every two years, were published on Wednesday. There isn’t much to cheer. Only 35% of fourth graders rated proficient in reading, which is about the same as in 2009. Worse,...