DALLAS -- A Texas teacher faces sexual assault charges after evidence of a sexual relationship with student surfaced, WFAA reports The 14-year-old boy at the center of the controversy at Quintanilla Middle School in Dallas is suspected of extorting thousands of dollars from the teacher.Police say 30-year-old Sandy Doan had a sexual relationship with the student."He commented that he was smitten with this pretty teacher," said the boy's uncle.Court documents state Doan talked to police."She confirmed that the student received an image of her exposing her breasts and they had engaged in explicit text messages," documents say.But police say it went further, and the two of them had sex at least three times since July of 2015.The boy's mother found the messages."And lo' and behold, she got her text on her phone stating that my nephew and this teacher were having a relationship," the teen's uncle said.The boy's mother noticed he suddenly had a lot of money. Police say the teen started extorting money from the teacher.The arrest affidavit states the teen sent Doan a text message in January of 2016 demanding money: "Aint b'sing watch ima start getting the pics and everything ready to show the cops. Right i aint playing.""He would need money, and he would just call her and ask for more. She would drop it off for him, and you know, he would pick it up and be gone for 2-3 days at a time," the boy's uncle said.Police say the teacher paid the teen about $28,000. The family says the boy would use the money for alcohol and drugs. His mother went to the principal."She requested that the school tell the teacher to stop providing money to her child as he was using it for illegal purposes and causing issues at home," court documents said."He got a free piggy bank an easy piggy bank, and he continued asking for these favors," the uncle said.Doan was arrested Friday and charged with sexual assault and is on administrative leave. The student most likely won't be charged with a crime for taking the money.