The news was confirmed by St. Paul education superintendent Glen Brodziak.
"We are absolutely devastated and our deepest condolences go out to all the family," he said.
The girl, a Grade 6 student at Racette Junior High School, is not being identified.
Richard Edward Benson, 46, who lives in the St. Paul area, was charged with three counts of dangerous driving causing bodily harm, one count of resisting arrest and one count of possession of marijuana.
He will appear in provincial court Monday and remain in custody until then.
CBC News has learned Benson has a lengthy criminal record, dating back to 1992, which includes several driving offences.
He is scheduled to go on trial in April for a dangerous driving charge from April 2011.
Suspect co-operating with police
Police are still waiting for analysis on a blood sample taken from the driver, which may lead to further charges, said RCMP Chief Supt. Randy McGinnis.
But police may never learn how fast the minivan was travelling because falling snow made taking measurements difficult, he said.
Benson, who was "combative" when arrested, is now co-operating with police, said McGinnis.
"This morning he was very remorseful, very apologetic of what has transpired and co-operated fully with our investigation," he said.
Ralph Benson, brother of the accused, said that Richard suffered from seizures ever since he was badly beaten in Mayerthorpe a decade ago.
The beating left him in a coma. He has a plate in his head and takes medication for seizures.
"Right now he should be inside of a hospital," Ralph Benson said. "Not sitting in a police cell."
Richard can be disoriented when he comes out of a seizure, which could account for his "combative" nature with police after the crash, his brother said.
"I mean he's fighting for his life when he comes out of that seizure," Ralph Benson said. "He's had seizures here with us and it is a very freaky situation … he goes like into a convulsion. His muscles spasm, his muscles cramp up on him."
Benson said that Richard had a seizure as recently as Sunday. In an interview with The Canadian Press, Benson said that Richard was cleared to get his driver's licence back several years ago.
"We feel horrible. I mean we have children too. We have family," Ralph Benson said.
Three Grade 6 students were left in critical condition and five others injured after the minivan crashed into the school Thursday morning.
Two students remain in hospital in Edmonton.
3 students pinned by minivan
Police said one child was pinned against the wall while two others were pinned while sitting in their desks.
The scene was chaotic as police and firefighters fought with the suspect while trying to rescue students, said McGinnis.
"There was a huge issue with safety because this vehicle came to rest on the desks in the classroom and there was great fear the vehicle may have tipped, come off the desks and land straight on top of the students that were underneath," he said.
"The staff at Racette school were paramount in keeping him in the vehicle and not rocking the vehicle off the desks onto the students," he said.
Witnesses told CBC News that before the crash, a white minivan was racing through back alleys in St. Paul.
The vehicle left the road and drove into the side of the classroom where Grade 6 students of Racette Junior High School were taking French. The class was being held in the old Glen Avon School building.
The school was closed Friday to allow officials to evaluate the structural integrity of the building.
Classes will also be cancelled Monday and students will be relocated to the high school Tuesday, said Brodziak.
In the meantime, people in the community are trying to deal with the tragedy. A vigil is scheduled at the school for 5 p.m. today.
"I just pray for the kids …fighting for their lives," said Sandra Duquette, one of the organizers. "I pray for their families. It's just touched the whole community. We will be here at 5 o'clock definitely to light the candles."
St. Paul is about 200 kilometres northeast of Edmonton.