James Quigley, who was arrested Thursday night, also has been charged with sexual assault.
Police say a 16-year-old female student reported that Quigley, 34, had harassed her after he obtained her email address and cellphone number in March. According to an affidavit, investigators have copies of messages she received.
The student said Quigley had threatened her and parked in front of her house "on multiple occasions for no reason," according to the affidavit.
He tried to persuade her to sign a contract that promised her good grades if she would keep the messages secret, the affidavit stated. The student said Quigley did not want his wife, who is also a Richardson High teacher, to find out about the messages.
The girl said she refused to sign the contract but eventually had sex with Quigley twice at her home between May 1 and June 30, according to the affidavit.
Richardson High principal Charles Bruner sent letters to students' parents Friday to notify them of the allegations.
Quigley, who has taught at the school since 2009, has been placed on administrative leave by Richardson Independent School District. He remained in the Dallas County Jail on Saturday in lieu of $100,000 bail - $50,000 per charge.
Anyone with information about the case may call police at 972-744-4800.
