Results from a closely studied comparative international assessment made headlines late last year for exposing the United States’ continued middling performance in science among developed nations. However, the full findings from the study, which took measurements from over half a million 15-year-olds across the globe, are still being released. Analysis from this week’s international report on student well-being, for example, appears to be in tension with a statement put out by a leader of one of the U.S.’s most powerful teachers’ unions.

The Organization for Economic Co-operation and Development, or OECD, is an intergovernmental group that grew out of the post-WWII Marshall Plan. The organization administers the Programme for International Student Assessment, or PISA, to a representative sample of students in over 70 participating countries every three years. Early findings from the 2015 administration of the test first appeared last December, and focused most in-depth on student achievement in science. The portion of the report released this week focuses more on non-academic quality-of-life statistics.

The top-line student achievement numbers released late last year did not include major surprises for those familiar with the United States’ historically-average performance among other wealthier nations. While Singapore led in each category, the United States ranked 40th among the 72 participating nations in math, 25th in science, and 24th in reading.

The bad news for American educators is that the PISA scores for U.S. students did not show any improvement in reading or science, while math scores have actually slipped since 2009. The good news is that U.S. students appear more interested in science than their international counterparts, and the nation has made strides in closing socio-economic achievement gaps.

The most recent findings, released this week, show that American 15-year-old students, like many around the world, report an overall high level of satisfaction with their lives. On a scale of 1 to 10, the average U.S. student rated their quality of life at a 7.36, in line with the OECD average of 7.31. The nations with the happiest students were Mexico and Costa Rica.

One wouldn’t necessarily know that American students are mostly happy by reading the reaction issued by Randi Weingarten, the influential president of the American Federation of Teachers. In her statement, Weingarten, who is a vocal opponent of over-testing, wrote:

“Nearly 68 percent of U.S. teens reported testing anxiety, higher than the OECD average of 55.5 percent. By contrast, 45.1 percent of Polish teens reported feeling testing pressure. In 2000, Poland made significant changes in its public education system, including using tests only to inform instruction. Poland is now among the top-performing nations.”

While those numbers are accurate, they don’t tell the whole story. Though U.S. teens do report above average testing anxiety, it’s not clear that the metric is particularly important for determining a student’s quality-of-life, or a school’s non-academic qualities. Polish teenagers, for example, may be less stressed over assessments, but they also report a lower level of life satisfaction than the average at 7.18, on the 1 to 10 scale.

Furthermore, Andreas Schleicher, the OECD’s top education official writing in an editorial that accompanied the report, found that the number of hours a student spends studying is unrelated to their reported quality-of-life, “and while educators often argue that anxiety is the natural consequence of testing overload, the frequency of tests is also unrelated to students’ level of school-work related anxiety.”

A better predictor for student happiness, according to Schleicher, is how well connected students feel to their teachers, their parent’s level of engagement in their lives, and whether they get regular exercise. The researcher argued that schools should focus on fostering positive learning environments and combating bullying, which remains a problem in schools at home and abroad.

The students’ well-being survey also raised concerns for Schleicher about the amount of time teenagers spend on the Internet. In his editorial, he said that “extreme Internet use” of more than six hours in a day is on the rise, and is associated with a negative impact on a students’ well-being. Internationally, 26 percent of students engaged in extreme Internet use on the weekends and 16 percent spent at least six hours online during the average weekday.

For each of the findings, including the top-level results that suggests mediocre performance for America’s students in core subjects, it’s worth remembering that the OECD disproportionately focuses on economically advanced nations. For example, not a single sub-Saharan African nation was included in the 2015 survey. If a more representative sample of world nations were used, American academic performance and happiness measures would likely appear comparatively stronger.

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