A married history teacher has been arrested after he prompted girls to perform sex acts and send him lewd images in exchange for higher grades.
Casey Hauff, 32, of Atoka, Oklahoma, faces 11 sexual abuse charges.
Five alleged victims have come forward and authorities fear that there could be more.
Hauff taught at Atoka High School until he resigned when the sexual abuse allegations were made.
Police said the victims only came forward once a classmate told school authorities.
A relation of one 16-year-old alleged victim told Fox News: "He was tutoring her to bring her grades up.
"If she did this she would get an A, and if she did this and so on. And she had sent him pictures of her in her bra and panties.
"I told her [by coming forward] you're saving everybody."
Gene Dobson, Atoka police chief, said the town was "emotionally charged" over the allegations.
"Many of the sexual acts occurred at the school during school hours. [Hauff] also requested several of [the victims] send nude photographs of themselves to his cellphone," he said.
Hauff has been accused of rape, solicitation of a minor, sexual battery, forcible sodomy, showing obscene material to a minor, and lewd or indecent proposals to a child under the age of 16.
Hauff has been released on $250,000 (£156,000) bail.
A similar incident was reported earlier this year where a 55-year-old maths teacher, Jonas Magdangal, drove a 17-year-old victim to a hotel for sex.
Magdangal gave the female money and an 'A' to keep her quiet. The teenager is wanted by police for extortion.