Students do not have to spend a summer abroad for an essay-worthy experience. When Mary Lang Gill was a rising senior at the Atlanta Girls School, a private school, she hired Pam Proctor, an independent college counselor and the author of “The College Hook,” a college admissions guide. After learning that Ms. Gill loved to paint, Ms. Proctor connected her to the Florida Highwaymen, a band of renegade painters active during the 1950s and ’60s.

“I spent a whole day with them,” painting and observing, said Ms. Gill, who just graduated from Dickinson College. “It was one of the coolest things ever, and I love that and I got to put it on my application.” Ms. Proctor said she spent a great deal of time with students helping them find the right topic for the college essay. “Picking the essays is as important as writing them,” she said. After that, she said, the stories “write themselves.”

As colleges look for specialization, “mastery” and “passion” have become buzzwords at many New York City private schools. Along with the perception that perfectly developed essays are essential is the sense among some parents and teachers that colleges have shifted from valuing balanced students who excel in several areas, like history and ice hockey, to demanding students who perform well across all subjects and have an area of “mastery,” like squash or fencing, that showcases one’s depth.

“Colleges have moved people from thinking they should be exceptionally well rounded to using the vocabulary that ‘well rounded’ means ‘no edge,’ ” said Bruce Poch, the former dean of admissions at Pomona College.

Mr. Poch said members of his office staff sometimes joked that they were witnessing the “complete disappearance of summer jobs,” especially among upper-income applicants who opted for “decorative” internships at places like investment banks, where they could work with friends of their parents. He said further evidence of overspecialization was the disappearance of the multisport athlete. “It’s all but vanished,” he said.