It's not quite as simple as your article suggests. A student made a comment that, out of context, could be construed as a threat and a news station called the sheriff's office. Two deputies were sent to the kid's house to investigate, which they did, with permission.
Looking at the Allen Parish Sheriff's Office Facebook page, I see that they shared the following article, which says:
"The whole notion that there was a SWAT raid over a math symbol is absurd," [Allen Parish Sheriff Doug] Hebert told PJM. "I got a call from a KPLC that they had a serious threat of a shooting at the school, so we went to the house to verify. There was no search warrant, we just sent two [deputies] to knock on the door," chuckled Hebert. "This is a small parish and everybody knows everybody and we found out very quickly there was no crime and no threat."
In spite of that declaration, the student is facing expulsion. In the wake of the shooting in Florida the school board set a new policy. According to KATC, "Any student accused of talking about guns or school shootings will be investigated by three entities: the school board, the sheriff's department, and the district attorney's office."
Hebert's office is under major fire nationally and his phones are ringing off the hook. "It's crazy," he continued. "I've had to take down a Facebook posting I made informing the public what happened because my page will never become a place for political debate. That would impede my ability to inform my citizens." Hebert is concerned that this story has been blown way out of proportion, mostly by media spreading unverified information.
Student Faces Expulsion After Saying a Math Symbol Looks Like a Gun
According to a comment on the Facebook page made by the sheriff's department:
This is an excerpt of the actual tip that was forwarded to me by a news reporter: I would like to report that a student (name of student redacted) at Oberlin High School allegedly made threats to several high school students about shooting them at school tomorrow
It's also relevant to note that the removed Facebook page is probably this page: https://www.facebook.com/allenparishso/posts/1801435039878169, which is also linked to by your article. Although it's deleted, you can read the full post here. (We can confirm that's what the page said by quickly performing Google searches before Google updates its results, and seeing that page pop up as a result, like this.)
Lastly, I'll also note that the KATC article reports:
"The students were working together, and a student made a math symbol of a square root sign, which kind of looks like a pistol. And he was helping a weaker student, and the student says, 'Well, that looks like a pistol!' And he just made a comment [like] 'let's just get to work before I shoot you with a pistol," said Superintendent Doucet.
