LUFKIN, Texas -- A Texas teacher is behind bars on child sexual assault charges after she admitted to having sex with four high school students - two of them at the same time.

The Lufkin News reports that 38-year-old Heather Lee Robertson of Lufkin, Texas was arrested on Saturday after admitting to the crimes.

The school system received information about the incidents on Thursday that alleged that Robertson had been sexually involved with several students. Police questioned each student they could find about the allegations and were told by one that the teacher had begun chatting and sexting with students shortly after spring break.

That student said he was soon invited to her apartment for sex. He told her he was bringing a friend with him and she agreed.

The newspaper reports that after speaking with them for several minutes, Robertson led them to her bedroom while taking off clothes. A warrant received by the Lufkin News said that the kindergarten teacher had sex with both teens at the same time.

The two teens said there were two others who had possibly been sexually involved with the teacher. Upon speaking with them, one said he would speak out of his home and Robertson would pick him up. That victim said they had become friends on Snapchat before she eventually invited him over.

When police confronted the teacher, she admitted to having sex with students - some as many as four times - beginning in late 2016. She also did not "require" the boys to wear a condom adding that she was no longer able to have children.

The school system accepted Robertson's resignation, per protocol, Thursday afternoon. According to jail records, Robertson now faces charges six counts of improper relationship between educator and student and six counts of sexual assault of a child - both second-degree felonies.

If convicted, the now ex-teacher faces 20 years in prison.