A Texas kindergarten teacher is facing charges after she admitted to having a threesome with two high school students.

According to the Dallas Morning News, Heather Lee Robertson, 38, admitted to having sex with four students in total, and with two of them simultaneously. She also reportedly did not ask the minors to wear a condom since she said she unable to become pregnant.

Police reportedly began an investigation after receiving a tip, and questioned the minors believed to be possible victims.

According to the arrest warrant affidavit obtained by the Dallas Morning News, Robertson had sexual relations with four students at her apartment in Lufkin; she admitted to having sex with one student four times while another student reportedly said he, too, had sex with her multiple times.

In one instance, just after spring break, Robertson began exchanging sexually-charged messages with a student on Snapchat. She eventually invited him to her home and he asked if he could bring a friend. She agreed, and had sex with both of them.

Robertson reportedly said she had been drinking heavily of late and could not recall the details of all the encounters. According to the Daily News, Robertson was arrested in March on a DUI charge.

According to the Dallas Morning News, Robertson remains in custody after her arrest last week, and has resigned from her job. She could face up to 20 years in prison if found guilty.