Oklahoma teacher Hunter Day was waiting for candle-lit dinner with student

An Oklahoma teacher is accused of having sex with a high school student after the boy's parents reported nude photographs and text messages on their son's phone to authorities.

Hunter Day, a 22-year-old teacher at Yukon High School in Yukon, Oklahoma, US was arrested on Wednesday after authorities said they used the boy's phone to confirm a meeting and found Day sitting on her living room floor with the lights off and candles lit.

Day, who officers say admitted to having a sexual relationship with the boy, is charged with rape in the second degree, possession of child pornography and soliciting sex from a minor using technology, Canadian County Sheriff's Office officials said in a statement posted on Facebook. Day is being held on $85,000 bail.

"This is a classic case of a serious breach of public trust," Canadian County Sheriff Chris West said in the statement. "School teachers are entrusted to protect and educate our children, not to engage in an unlawful sexual relationship with them."

Authorities said they were made aware of the alleged relationship after receiving a complaint from the boy's parents, who were worried that their son had already had sex with the teacher - and believed at the time that she was his chemistry teacher. It is unclear whether Day, who taught science, actually taught the student.

The parents asked investigators to conduct a forensic review of their son's phone, officials said. Investigators say they discovered evidence that Day and the boy already had sex and had made plans to have sex again at her home on Wednesday. Using the boy's phone, investigators sent Day a text message confirming the meeting. Day said "yes," officials said.

She also told the boy to hurry up before her husband got home, officials said.

When investigators arrived at Day's home, they sent a text message from the boy's phone that said "I'm here," officials said. Day responded with a message that read, "the doors unlocked as usual." Investigators opened the door and identified themselves.

Officials said Day fully cooperated and admitted to the sexual relationship, as well as sending photos of herself in her bra and panties. She said she had received photos of the boy's genitalia.

Day's attorneys could not be immediately reached.

Day was hired to teach science at Yukon High School at the beginning of the school year, according to an October report by Oklahoma City-based News 9. She was among the state's 1500 emergency certified teachers hired without education training to help mitigate teacher shortages. It's one of many ways Oklahoma is dealing with a deepening budget crisis that has forced class sizes to surge, art and foreign-language programs to shrink or disappear and - in many districts - schools to operate just four days a week.

News 9 reported that Day had little to no teaching experience. She held a degree from Oklahoma Baptist University and at one point planned to go to medical school. Day had a 10-month contract to teach at the school, but said she planned to get her certification requirement so she could return next year.

Emergency certified teachers are filling classrooms in Oklahoma from pre-K through high school, and attend training throughout the school year that help them handle student behaviour problems and other classroom issues, News 9 reported.

"I think my biggest concern when I first travelled down this route was behaviour management," Day told News 9 in October. "I was worried that I wouldn't be able to manage the kids or that they would look at me and see how young I am and think 'Oh, well you're just a kid too and I don't have to listen to you'."

Yukon Public Schools said in a statement Thursday that officials conduct background checks on employees before hiring them, and that nothing alerted them of Day's alleged behaviour. The school district is cooperating with authorities and can't release additional information about the incident while its investigation remains open.

News 9 reported Thursday that Day's husband is a football coach at the school.