Sparks Middle School, outside Reno, remains an active crime scene, school officials said in a Twitter post.
Two minors are in critical condition at Renown Regional Medical Center after the shooting, a hospital spokeswoman said.
Authorities released few details about the incident, but city officials said in a statement that the suspect was "neutralized."
"Law enforcement assures that the school and community are secured at this time," the statement said.
City officials said authorities received emergency calls from students and staff at the school about 7:15 a.m. about an active shooter on campus.
Authorities said students were being taken to a nearby high school to meet their parents. School was canceled for the day at Sparks Middle School and nearby Agnes Risley Elementary, officials said.
"I was deeply saddened to learn of the horrific shooting at Sparks Middle School this morning," Nevada Gov. Brian Sandoval said in a statement.