JACKSONVILLE, Fla. -

An upset and frazzled father is asking other parents to help him figure out who assaulted his daughter.

He said someone punched her in the back of the head in the Englewood High School hallway Thursday between classes.  The sophomore was hospitalized with a concussion.

The girl was brave enough to return to school Friday, the back of her head still bruised.

Her father, Bill, was at his desk Friday but not able to work, focusing only on his 16-year-old daughter, whom Channel 4 is not identifying.

"There's nothing else a father can have than to have his child hurt like that," Bill said. "So this has just been the worst time of my life."

He described what his daughter said happened.

"It was just out of the blue," Bill said. "The guy came up behind her and struck her and called her a vulgar name and ran off."

He said his daughter looked back as she was falling and saw a boy in a gray hoodie. She landed on the hallway floor and suffered a concussion.

"It's probably harder on me than it is on her because as a parent, you love your child, and to have someone hurt your child and harm them," Bill said.

He said his daughter has no idea who would hit her or why. Bill said she's a good, peaceful, quiet kid with a steady boyfriend, and she doesn't drink, do drugs or hang with the wrong crowd.

Her dad is trying to figure out if the attack was gang-related, part of a disturbing new teen trend called the "knock-out game," a case of mistaken identity, or someone being just plain mean.

"Our children are supposed to be our future and our hopes," Bill said. "We're supposed to give that to them, and I feel like we're missing that as a society, that this violence in the school that people are having in the school, I don't get it."

Bill is pleading with other Englewood parents to talk to their kids.

"You're going to put your son down and he's going to put his head down on the pillow, and you're going to give him a kiss and tell him that you love him," Bill said. "I'd ask you also to ask him if he assaulted my daughter, if he was wearing a gray hoodie on Thursday. And I hope he's man enough -- my daughter would take your apology and this would end. So if you're man enough to apologize to her, that would be the end of it. Please have enough decency to do that."

The school knows about the incident, and a spokeswoman for the school district said officials are looking into it.

Englewood has cameras in the common areas of the school, but not in the hallways where the assault took place.