Police and fire crews blocked off several surrounding streets while Bentonville's Bomb Squad and K-9 units searched the school.
"It sounded like a young boy on the phone, asked for one of the principals, when the principal wasn't there, they said that there was a bomb in the bathroom and that a student had put it there and then disconnected the phone... This kind of stuff is not funny at all," said Lt. Derek Hudson with Springdale Police.
The threat was called in a little after 2 o'clock Friday afternoon, so students and staff evacuated to neighboring Shiloh Christian.
"If something happened, you'd regret it the rest of your life and it's unfortunate we live in a day where things do happen."
After a shooting at Sandy Hook Elementary claimed 26 lives, Southwest and Shiloh decided to take their emergency strategies a step further.
"They had a prearranged plan, a partnership with Shiloh Christian school where if anything would happen at either school, that they would use the other... The reason that Southwest and Shiloh formed this partnership, was because of what happened in Connecticut a couple years ago," said Rick Schaeffer with Springdale Public Schools.
In Friday's case, Southwest was deemed safe and no suspicious items were found, but the district will keep reacting to every risk.
"You would rather get them out of the building and find out later there was no threat, than make a mistake," said Schaeffer.
Meanwhile, police will keep searching for the caller.
"We do take these things seriously. We've called our detectives out here. They will investigate this thing, continue to investigate it in the coming weeks until we find out who's responsible for this and you can face criminal charges," said Hudson.
If parents wanted to, they were able to pick up their kids early from Shiloh Christian. Other students went back to class until school let out and bus routes ran as usual. Also worth noting, Schaeffer said every school in Springdale does have an emergency plan in place.
Copyright 2016 Nexstar Broadcasting, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.