Ventura County sheriff's deputies responded to the scene around 11 a.m. after receiving a call about a man armed with a black semi-automatic handgun.
No details were immediately released about the arrest. Deputies said earlier that they were searching for a man wearing a green soccer shirt, green shorts and a black backpack.
Students at Peach Hill were dismissed for the day. Parents were told to pick up their children in front of the school on Christian Barrett Drive.