A new study that indicates low-income teenagers in Boston who hold summer jobs are less likely to engage in violence was hailed by the mayor and other community leaders as proof that youth employment programs can change people’s lives.

For the study, researchers at Northeastern University’s Center for Labor Market Studies polled 421 teenagers and young adults who found employment last summer through a youth violence prevention collaborative overseen by the State Street Foundation, the charitable arm of the Boston financial services company.

In confidential questionnaires, 3 percent of youths reported threatening or attacking someone with a gun during the month before starting their jobs, said Andrew Sum, a Northeastern professor and director of the market studies center.

When the job program ended, less than 1 percent said they had done so in the previous month, Sum said.