A former teacher who fled to Mexico with a 13-year-old student with whom she was having a sexual relationship was sentenced Monday to six years in federal prison.

Kelsey Peterson, 26, had pleaded guilty in July to a charge of transporting a minor across state lines to have sex and avoided a similar charge that would have carried a mandatory 10-year minimum sentence.

She will be credited for time served but will not be eligible for parole.

The guilty plea does not mean Peterson is off the hook on Nebraska state charges, which include kidnapping and first-degree sexual assault. Her attorney said he hoped those charges will be dropped.

Peterson and her relatives cried as they waved to each other across the courtroom and said, "I love you" after the hearing.

She started having sex with the boy when he was 12 years old and a student at the middle school where she taught in the south-central Nebraska town of Lexington.

Peterson's attorney, James Martin Davis, had publicly questioned the boy's birth certificate. Davis said the boy was likely at least 16, and that he was the aggressor.

Amy Peck, attorney for the boy and his family, bristled at the suggestion.

"He was a 12-year-old boy and the defendant knew it," Peck said in July, after Peterson's guilty plea.

Peterson was the boy's math teacher at Lexington Middle School during the 2005-06 school year, then started having sex with him in November 2006, according to court documents.

She and the boy disappeared in October, soon after the school district's superintendent confronted Peterson about allegations of an inappropriate relationship with the boy.

Peterson was arrested a week later in Mexico after the boy called his family.

The Associated Press previously named the boy as police were searching for him but stopped using his name after authorities charged Peterson with a sex crime.

The boy was an illegal immigrant at the time but has been granted humanitarian parole by the Department of Homeland Security.

Peck has said she plans to seek a visa that could put the boy and his parents on the path to citizenship.