Even a handful of poorly designed programs, Caruso notes, could cause educators who are just warming up to the idea of a social-emotional curriculum to dismiss the entire field. Critics already charge that social-emotional programs are a kind of “therapy light” and a waste of valuable classroom time. In 2010, a report from the U.S. Department of Education that evaluated seven different S.E.L. programs found no increase in academic achievement and no decline in behavioral problems. S.E.L. supporters criticized the study’s methodology and pointed out that the researchers couldn’t be sure that the comparison schools weren’t using S.E.L. techniques even if they weren’t using a formal program. Still, to show that S.E.L. is effective, Caruso says, programs will have to be tested the same way a new pharmaceutical is: through a randomized trial that could distinguish short-term placebo effects from lasting improvements. Without such evidence, social-emotional learning could go the way of the self-esteem movement, an ill-fated program from the 1980s in which schoolchildren repeated mantras like “I am special” and “I am beautiful.” At the time, it, too, was considered the height of progressive education. The program was largely abandoned after it ended up being connected to rising rates of narcissism.

“It’s a big messy field, with a lot of promises, but very little data,” Caruso says of S.E.L. “Right now I think people are just throwing stuff at the wall to see what sticks.”

One of social-emotional learning’s “stickiest” programs is Second Step, the plug-and-play curriculum that provides teachers with grade-appropriate emotional-skills lessons. Originally developed as a violence-prevention program in 1986, Second Step is currently used by approximately 25,000 schools in the U.S. and Canada, according to Joan Cole Duffell, executive director of Committee for Children, the nonprofit behind the program.

At Ella Flagg Young School in Chicago, I sat in on a sixth-grade Second Step class taught by Latasha Little-Brown, the dedicated “social-emotional learning coordinator” who has worked at the school for nine years. That day, Little-Brown began by playing a Second Step video featuring good friends, Lydia and Maria. In the story, Maria’s aunt gives her a cool new necklace, which has beads made of paper. Lydia loves it, so Maria lets her borrow it. But as Lydia is walking back from the party, it suddenly starts to rain and the necklace is ruined. Lydia doesn’t know what to do.

In the teachers’ edition of the exercise, the goal is for students to write out the steps of an apology, including reparation. (Step 1: “Maria, I was wrong for taking the necklace and not caring for it properly.” Step 2: Offer to pay for the necklace.) Little-Brown nudged the students in this direction, until one boy — a chubby kid who had kept his jacket and backpack on during the entire class — finally raised his hand in frustration. Lydia hadn’t been negligent, he pointed out: she’d just been walking home and got soaked by a thunderstorm. How was the loss of the necklace her fault?

Lawyering ensued. One girl insisted that Lydia could have put the necklace in her pocket, or balled it up in her hand — leading another student to argue that just clutching the necklace in a downpour wouldn’t have protected it. Meanwhile, Backpack Boy was still trying to parse the details of friendly obligation. If someone dumped a bucket of water on you as you walked by, he wanted to know, would that be your fault? What if someone robbed you or threatened you with a gun?

Little-Brown allowed the debate to go on for several minutes, then moved crisply to the official point of the lesson: that once a thing is in your possession, you are responsible for it. The class ended with each group writing the steps of restitution on a piece of poster board. It was a disappointing moment. Though Little-Brown was engaged and thoughtful, the class still felt more like a rote exercise in social obligation than a nuanced exploration of a complicated issue. It was hard to believe that the resolution was satisfying to someone like Backpack Boy — one of the few students who seemed eager to wrestle with the knotty issues on which justice can turn.