Reading, writing, arithmetic—and grit and gratitude? A growing number of students and schools may start receiving grades for the two Gs, plus other so-called noncognitive traits, thanks to a recent update to the federal Elementary and Secondary Education Act. The new law requires states to include at least one nonacademic factor in their school evaluations. This year nine California school districts started including progress in social and emotional learning (SEL), as reported by students on questionnaires, in rating their schools. Other districts are considering following suit.

No one questions that building skills such as self-control, perseverance and conscientiousness can help children thrive. A 2011 meta-analysis of 213 of the best evidence-based SEL programs found that they led to significant improvements in social and emotional skills, behavior, attitudes and schoolwork. “It's what people want for their kids,” notes developmental psychologist David S. Yeager of the University of Texas at Austin. But some researchers, like Yeager, who study noncognitive traits, are expressing real concern about the trend to test them and hold schools accountable.

For one thing, tests that measure qualities such as grit and persistence were designed for use in research settings and not as part of a high-stakes measure of student growth and school performance. “They weren't created for this purpose,” warns Angela Duckworth, a psychologist at the University of Pennsylvania who developed a widely used eight- to 12-question test called the grit scale. Her research has shown that a high score on grit can predict success better than IQ in a variety of settings—from upping someone's chances of graduating from high school to winning the national spelling bee.

That said, teaching things like grit via a lesson plan can be tricky. “The question of whether character can be learned is unambiguously yes,” Yeager says, and kids absorb lessons from their social environment all the time, “but intentional efforts are far less successful than unintentional ones.” Duckworth has experimented with using cartoons and videos to give middle school kids accurate information about deliberate practice, hard work and managing frustration. The results were modest: the program raised grades over just one marking period and only among low achievers. “I don't think grit is the best predictor of all kinds of achievement,” says Duckworth, whose first book, Grit: The Power of Passion and Perseverance, was published in May.

Indeed, a recent study conducted by Kaili Rimfeld of King's College London and her colleagues found that grit had only a small effect on how well 16-year-old twins performed on standardized tests given in England and Wales. Rimfeld is skeptical of efforts by the U.S. and the U.K. departments of education to prioritize teaching noncognitive traits. Research has yet to prove that such “intervention programs” are helpful, she says.

Another serious problem with holding schools accountable for noncognitive learning is that progress can be hard to assess. Schools that provide strong social and emotional development tend to produce more self-critical students, who will rate themselves lower on SEL questionnaires. “It's just the humility that comes with expertise,” Yeager explains. Last year Duckworth and her colleagues found evidence of this kind of reference bias in a study of more than 1,300 Boston eighth graders. Those at higher-performing charter schools deemed themselves less conscientious, less self-controlled and less gritty than lower-achieving peers at district public schools. When the scientists tracked individual classes over three years at two charter schools, they found that self-measures of noncognitive skills plummeted. The kids appeared to be holding themselves to a higher standard.

“You can't make high-stakes decisions based on measurements that can actually be wrong in the wrong direction,” Yeager says. “You reward the people who are the worst and punish the people who are the best.” A growing body of research shows how noncognitive abilities help children become happy, successful adults, Duckworth adds, but it is a misstep to then include them in school-accountability systems—now or maybe ever. “I just don't think carrots and sticks have been so effective in character development in the past,” she says, “and I don't expect them to be all that helpful in the future.”