CHARLOTTE, N.C. – A string of possible school threats popped up across Charlotte-Mecklenburg Schools this month.

On Friday, there was heightened security at South Mecklenburg High School after a concerning message surfaced earlier in the week.

It comes after police investigated similar cases at two other schools just this month. One police report was taken at Walter G. Byers Elementary School and another incident happened at Ridge Road Middle School.

Fortunately, authorities say none of the threats were considered credible.

The principal of South Mecklenburg High School said it apparently began as a practical joke but it caused concern among students.

“I heard somebody was going to shoot the school up,” says junior, Jaylen James.

James was so concerned he thought about missing school.

“I felt like I shouldn’t come, I came though,” James told NBC Charlotte.

Authorities determined the threat was not credible. The principal said there was an alleged connection between a photo sent through the smartphone feature, Air Drop, and a warning message supposedly found at the school.

Parent, Jilly Ivy, said the school kept her in the loop.

“I think South Meck does a great job taking care and keeping our kids safe, so I feel comfortable sending them to school,” Ivy told NBC Charlotte.

On the same week, police investigated another case at CMS. According to the police report, it involved a discussion over the internet about doing a school shooting.

The report was taken at Walter G. Byers School but there were no specific threats against the school or any school at CMS, police said.

In a third case, jokes were being thrown around by third parties that a suspect was going to “shoot up the school” at Ridge Road Middle School, according to a police report.

Authorities say none of the threats in those cases are considered credible.

“It’s sad that our kids have to hear about that and it’s a worry in their life,” Ivy said.

“You just got to live through it,” James said.

Police are not saying whether charges are possible in the case at South Mecklenburg High School. The principal said those involved are being held accountable.