“Will an overstuffed profile become a must?” asked a review of LinkedIn by Common Sense Media, a nonprofit children’s group. “Also, is it even healthy for kids to be so future-focused?” Teenagers, the site concluded, “should think twice before posting an online résumé.”

Professionalized teenage résumés could also further intensify disparities in college applications.

“Kids from privileged families tend to do more of those things both offline and online — joining school clubs, writing for their school newspaper, getting tutoring so their grades go up, doing SAT preparation,” says Vicky Rideout, a researcher who studies how teenagers use technology. Using LinkedIn on college applications, she says, “is yet another way for there to be a disparity between the haves and the have-nots.”

For high school students, LinkedIn is partly a defense mechanism against college admissions officers who snoop on applicants’ public Facebook and Twitter activities — without disclosing how that may affect an applicant’s chance of acceptance.

A recent study from Kaplan Test Prep of about 400 college admissions officers reported that 40 percent said they had visited applicants’ social media pages, a fourfold increase since 2008.

Officials at Vassar College and other institutions that deliberately do not search out applicants’ social media profiles suggested that colleges disclose their admissions practices.

“We prefer to evaluate a candidate based on the items that candidate has prepared and submitted to us,” said Art D. Rodriguez, Vassar’s dean of admission and financial aid. He added, “While we understand that some colleges and universities do look into candidates’ online profiles, we believe those schools should be transparent about the procedure and alert applicants to it.”

Some high school students are establishing LinkedIn profiles to give the colleges that do look something they would like them to find. Students who naturally tailor posts for their peers on Instagram, Twitter or Facebook told me they used the professional network as a separate space to market their accomplishments to adults.