Dawson County Attorney Elizabeth Waterman said Kelsey Peterson, a 25-year-old sixth-grade math teacher and basketball coach at Lexington Middle School, was arrested in Mexicali. Peterson and the boy fled after police began investigating whether the pair had an intimate relationship, authorities said. Court documents said the boy was last seen Oct. 26.
A judge issued an arrest warrant Monday charging Peterson with kidnapping, child abuse and contributing to the delinquency of a minor.
Peterson also faces federal charges, including transporting a minor across state lines or a foreign border for sexual activity, U.S. Attorney Joe Stecher said. Those charges were filed Thursday.
The boy, Fernando Rodriguez, was an eighth-grader at the school, but district Superintendent Todd Chessmore said Rodriguez had been in Peterson's 6th-grade math class.
Peterson's car crossed into Mexico on Tuesday at the San Ysidro Port of Entry, which separates San Diego and Tijuana, Mexico, Lexington police said. The car's license plate was captured by an automated system that scans the plates of all vehicles passing through the entry point.
Cars typically are not stopped on the way out because "our focus is on what's entering the United States," said Vince Bond, a spokesman with U.S. Customs and Border Protection in San Diego.
Court documents showed authorities had recovered several e-mails and letters in which Peterson and the boy professed their affection for one another.
Peterson also gave the boy a cell phone without his family's knowledge so she could reach him more easily.