The child, identified as David, is recovering from surgery at Phoenix Children's Hospital. He's stable, but still in critical condition.
The family says he sustained serious injuries to the back of his head, neck and lungs.
David is a 5th grade student at southwest Academy in Tolleson.
Officials say David was on the bus when he got out through a emergency exit while the bus was still traveling at about 15 miles per hour through a residential neighborhood.
There weren't any other children on the bus at the time, just David, the bus driver and a bus assistant, who the district says is there to help special needs students.
Phoenix Police are looking into what happened, but family disagrees with what investigators are saying.
"Nobody was able to stop him, there was the driver and another person on the bus and they were not able to get him before he got to the door," said Phoenix Police Lt. Kimberly Mitchell.
David's family doesn't agree. They say the bus assistant should have been able to stop David from getting out that back exit if he did jump up and go back there. They went on to say the bus assistant has actually threatened David in the past.
"I know my grandson and he wouldn't have done this, no. Nobody is that crazy to jump out of a moving vehicle unless you was forced out," said David Wise. "That's because this guy has been picking on him, how long do we have to tolerate this stuff?"
Was David scared of the aide and trying to run away?
"He wasn't scared of him.. it's called bullying," replied Wise.
There was a camera inside the bus, but there wasn't any tape inside the machine.
District officials tell FOX 10 they removed the tape on Wednesday to investigate another incident with the same student on the same bus, so there is no reporting of what happened on Thursday.
Meanwhile, the district says the bus assistant and bus driver are on paid administrative leave while during the investigation.
It looks like David has a long road of recovery ahead of him.