The Douglas County Sheriff's Office says they will not elaborate on the threat or who made it but say they are looking for someone.
Both schools were put on lockout because they are next to each other.
"I think anytime that you talk about a threat at a school, certainly there is a concern, but I think we're doing the right things, we're insuring our students inside the school are safe," Randy Barber with the Douglas County School District said.
Deputies say no one was injured and the students were allowed to leave school just before 3 p.m.
"We understand this is one of those scenarios that always causes an enormous amount of fear. We're trying to reduce that amount of fear as much as we can by having a high officer presence here," Sgt. Ron Hanavan, a Douglas County Sheriff's officer, said.
Parents did receive notification about the school being on lockout. Authorities say they may be at the school into the evening while they investigate the threat.