This summer, as last, Dylan Hernandez, 17, noticed a theme on the social media accounts of fellow students at his private Catholic high school in Flint, Mich.

“An awfully large percentage of my friends — skewing towards the affluent — are taking ‘mission trips’ to Central America and Africa,” he wrote to me in a recent email. He knows this from pictures they post on Snapchat and Instagram, typically showing one of them “with some poor brown child aged 2 to 6 on their knee,” he explained. The captions tend to say something along the lines of, “This cutie made it so hard to leave.”

But leave they do, after as little as a week of helping to repair some village’s crumbling school or library, to return to their comfortable homes and quite possibly write a college-application essay about how transformed they are.

“It rubs me the wrong way,” Hernandez told me, explaining that while many of his friends are well intentioned, some seem not to notice poverty until an exotic trip comes with it. He himself has done extensive, sustained volunteer work at the Flint Y.M.C.A., where, he said, the children he tutors and plays with would love it “if these same peers came around and merely talked to them.”