Wilkerson said there might be more injuries, as parents could have transported the students themselves.
The middle school was on lockdown as officers searched the area and found no threat.
Meade County was among the first school districts in Kentucky to implement the system.
At least one of the threats was made on Snapchat over the weekend.
Tamara Mouser resigned "effective immediately" after her arrest at TK Stone Middle School Tuesday morning.
In the last few minutes of session on Thursday, March 28, the Kentucky Senate passed Senate Bill 2.
The school safety bill would allow local school boards to hire and assign guardians at schools.
The investigation by Oldham County Police is ongoing.
It's the first Jefferson County Public Schools building to install and start training on the Evolv Express weapons detection system.
Shots were fired after a local football gave over the weekend.