A former Lexington, Nebraska teacher pleaded guilty Monday to two state charges for having sex with a 13-year-old student and fleeing to Mexico with him.

Dawson County Attorney Elizabeth Waterman says Kelsey Peterson entered the plea to two counts of first-degree sexual assault. Two other charges were dismissed.

Peterson had pleaded not guilty to state charges in November.

Authorities say Peterson was the boy's sixth-grade math teacher at Lexington Middle School during the 2005-06 school years and then started having sex with him in November 2006.

Peterson is already serving a six-year prison sentence after pleading guilty to federal charges. She faces up to 50 years in prison for each of the state charges. Her sentencing is scheduled for March 6th.