The Sacramento County Sheriff's Department said the stabbing happened on campus around 1:30 p.m.
A 16-year-old student was stabbed by another student in a bathroom near the school's football field.
The stabbing victim was hospitalized after leaving campus to call 911 at a nearby residence, according to a statement made by Principal Paula Duncan and sent to parents. He is responsive and sustained non-life threatening wounds.
Sacramento County deputies later arrested a 17-year-old student.
Law enforcement officials lifted the lockdown around 2:50 p.m.
According to the Elk Grove Unified School District, Smedberg Middle School, which is next door to Sheldon, was not locked down.
There was no information immediately available on what led to the stabbing.