This story, “Five years after Common Core, a mysterious spike in failure rate among NY high school students, was produced by The Hechinger Report, a nonprofit, independent news organization focused on inequality and innovation in education and based at Teachers College, Columbia University.

Back in 2013, when New York was one of the first states in the nation to adopt Common Core standards and administer tougher tests, children’s test scores initially plummeted. Then, as teachers had time to develop lesson plans and adjust to new curricula, student performance began to improve. A similar pattern seemed to be emerging among the state’s high school students, who are required to pass a series of exams, called Regents, to earn a diploma. After an initial drop in pass rates among eighth and ninth graders on a Common Core algebra exam in 2014-15, scores improved.

But now, after five years of high schools teaching to the Common Core standards (now slightly revamped and called Next Generation Learning Standards in New York), there’s a sudden spike in the high-school failure rate. More than 13,000 more students failed the algebra Regents exam in the most recent 2017-18 school year compared to the previous year, pushing the failure rate up from 25 percent to 30 percent, according to a December 2018 report by education policy consultant David Rubel. In the English Language Arts or reading exam, the number of failing students grew by more than 12,000 students, increasing the failure rate from 16 percent to 21 percent.

“It’s odd that there would be a decline at this point,” said Morgan Polikoff, a professor at the University of Southern California’s school of education and an expert in assessments.  “Most often the trend is that a new exam is implemented, there’s a ‘dip’ in performance. I don’t like calling it a dip because it’s a different test so it’s not really comparable. And then scores gradually increase over time.”

It’s unclear whether New York is an anomaly or whether other states with raised standards may soon experience a similar deterioration among older students. In California, scores dipped among 11th graders in the spring of 2018, four years after the introduction of Common Core aligned exams. Meanwhile, younger grades continued to post progress.

Some analysts have suggested that California’s high schoolers didn’t try hard on the exam because the scores didn’t matter for grades or college. But in New York, the exams are necessary for high school graduation. The question is why more students are struggling now.

Part of the answer might be small shifts in the high school population. Even if Common Core approaches are superior and teachers have mastered the new material, average scores could fall and the failure rate could rise when the share of low-performing students increases.

In New York, the number of “English Language Learners” in high school has been growing, according to Rubel. That’s a designation given to recent immigrants who don’t speak English fluently, and, historically, they tend to score below average. Indeed, 60 percent of English Language Learners failed the algebra Regents and 63 percent failed the ELA or reading Regents in 2017-18. English Language Learners accounted for 3,000 of the 13,000 additional students who failed the algebra test in 2017-18. But demographic changes don’t seem to explain why the other 10,000 kids failed.

These test results are pointing out that some students are having greater trouble learning the material than they used to. One hypothesis suggested by USC’s Polikoff is that low-achieving kids who were introduced to Common Core standards midway through their educational life might have been harmed in the sometimes rocky transition. The high school students who took the Regents last year were in third, fourth and fifth grades when Common Core was first introduced to them. Those are critical years to learn and master multiplication, division and fractions. Average and high-performing kids were able to cope with the new approaches.

“There’s pretty decent evidence that low performers didn’t do great in the transition to Common Core.” said Polikoff. “Common Core is more conceptual with math. If you don’t have the basics down, and the teacher is teaching in ways that seem more confusing, you could be worse off.”

Low-achieving children who are exposed to Common Core instruction from the start in kindergarten may test better in high school in the years to come. Perhaps this problem will be a transitional one that will work itself through the system in the next five years.

But Rubel argues that low-achieving students may continue to need more support with Common Core, especially students with disabilities and English Language Learners. He reasons  it would be straightforward to target extra support and tutoring to high school students who obtain the lowest “1” score on their eighth-grade state assessments, indicating that the child is not on track to be college ready.

“On day one, in ninth grade, every high school knows exactly how many students aren’t going to pass,” said Rubel. “You have a prediction system in place. Are we doing everything we can to give the kids who are behind the extra support they need?”

New York is one of a dozen states to require students to pass exit exams to graduate from high school. This past year’s class of 2018 was the first group of seniors who had to take the Common Core version of the algebra exam. (Previous classes had the option to take an earlier version of the math test.) A big question is whether the spike in Regents exam failures will translate into a first drop in the state’s graduation rate in 17 years. Those figures are expected to be released later in January 2019. But Rubel predicts that new graduation options, and a looser appeals system for students who fail, will keep the graduation rate steady.