Police have been investigating various threats made to schools across North Texas over the past few weeks.
In Little Elm and Denton officers got calls about armed students. In Rowlett, Hurst and Fort Worth, students made threats against others at school.
Grapevine police added two schools to the list Monday morning after bomb threats came in within 15 minutes of each other at Grapevine and Cross Timbers middle schools.
The schools' procedure is to evacuate when something like this occurs, and police said the students trained for such an event.
Students at Grapevine Middle School were moved to buses, while those at Cross Timbers were brought to Grapevine High School.
Police used K-9s to clear the buildings, but parents said text messages and phone calls from panicked kids sparked them to rush out to check on their children.
"Pure panic," Amy Cox said. "He was literally panicked, crying so I guess they just told them to get out of the school."
Despite the schools checking out OK, parents picked up their children in large numbers.
Police said they had a recording of the caller, and and said the call came from out of state. They don't believe it was connected to a student.
Officers said such a threat is a terroristic threat and is taken seriously.