The student was apprehended, according to a school statement that read, in part, "No weapons were used at any time during this incident."
Middle School South and Isaac Fox Elementary schools are on the same campus, 395 W. Cuba Road, and were placed on lockdown around 10:35 a.m. while police investigated, according to the School District 95 website.
Parents were kept aware of the situation via website messages.
"My initial reaction was just sick. Oh my god, what's going to happen? Are they OK?" Jamie Pecora, parent said.
"Your heart sinks. Just freeze in the moment," Debbie Webster, parent, said.
The lockdown at 12:20 p.m. for Isaac Fox and at 12:35 p.m. at Middle School South.