The fire broke out behind Bell Junior High School near Paradise Valley and Briarwood roads after 1 p.m.
Firefighters set up protective positions behind the school and across the canyon as the fire spread towards homes lining the canyon rim. At one point, a backyard fence and shed caught fire, but a San Diego Fire Department helicopter doused the shed with water from above.
The fire blackened a couple of acres in the canyon, but firefighters had it under control by 1:45 p.m.
No injuries were reported.
Anyone with information about the fire should contact SDFD.