A first-grade teacher in Washington state allegedly admitted to her husband that she cheated on him with a 16-year-old student — with whom she had sex in his truck, according to court documents.

Mackenzie Naught, 25, allegedly fessed up to her hubby Saturday night, just hours before being arrested on child sex crimes on Sunday, the Spokesman-Review reported. 

The educator from Whitman County said she became physical with the teen the week before in his truck during a meet-up in the dead of night, according to court docs.

Naught, who was friends with the boy’s family, was “being flirty” in Snapchat messages she allegedly sent to him on May 3 while her husband was asleep.

The teen was reportedly hesitant to meet up with the 25-year-old but eventually relented. He then picked up the St. John Elementary School teacher near her home around 2:15 a.m.

Naught allegedly asked the boy, who studies at the nearby St. John Endicott High School, to drive to a “little spot” where she suddenly kissed him, according to the docs. 

The two then allegedly had sex, and she told the boy not to tell anyone amid fears she could be busted.

Naught’s husband of four years told police that the boy also admitted to having sex.

The teacher was arrested Sunday and initially denied having sex with the boy when quizzed by cops — despite what she told her husband.

School officials put Naught on leave just eight months into her teaching gig, and she appeared in Whitman County Superior Court on Monday on a charge of first-degree sexual misconduct with a minor. 

“Our priority continues to be the safety, well-being, and support of our students and school community,” school officials said, responding to the allegations.

Naught’s arraignment is set to take place on Friday.