An Oklahoma high school valedictorian who is about to head to university on a full scholarship has been denied her diploma after using the word "hell" in her commencement speech.

In her speech Kaitlin Nootbaar referenced the fact she has changed her mind several times during her high school career about what she wants to do with her life.

After switching between wanting to be a nurse, then a veterinarian, Nootbaar said she now replies "How the hell do I know?" when asked what she plans to do.

In the written version she submitted to the school administration ahead of the ceremony, "heck" was used instead of "hell."

The line, which was similar to one from a speech in the film "Eclipse: The Twilight Saga" got a laugh from the audience, her father David Nootbaar told local news station KFOR-TV.

But when Nootbaar when to collect her diploma from Prague High School, no one was laughing.

"He said 'your diploma's right here but you ain't getting it. Close the door, we've got a problem,'" her father said.

The young woman, who has received straight-As all through high school, resulting in a 4.0 grade average, was told she had to write a letter of apology for using the word "hell" in her speech, if she wanted her diploma.

In the written version she submitted to the school administration ahead of the ceremony, "heck" was used instead of "hell."

Nootbaar's father said Kaitlin doesn't feel she should be required to apologize, and her family is supporting her decision.

"She was in every (extra) curricular activity, she's been with the Kiwanis, with the bank on the bank boards. If there's anything to do, she does it," her father said.

He added: "She's excelled beyond anything I would expect of her, being my child."

It isn't clear whether Kaitlin will be able to start college as planned, without the diploma in hand.

Local school board Superintendent Rick Martin declined to comment to the media.

"This matter is confidential and we can't publicly say anything about it," he told KFOR-TV.