Fairfax County Public Schools Superintendent Karen Garza announced her resignation from her post, according to a blog posted on the school system’s website.

Garza wrote she was leaving by Dec. 16 for a position as president and CEO of Battelle for Kids, a nonprofit education organization based out of Columbus, Ohio. The blog post was published on Monday, Sept. 19.

She said she was grateful for the opportunity to work with the school system since 2013. Garza said she would work with the school board and the leadership team to provide for a smooth, positive transition.

"It has been an honor and privilege to have worked with the dedicated and professional staff who make FCPS the finest school system in the country," Garza said. "I am so proud to have been a part of this outstanding system and this great community. I wish Fairfax County Public Schools much continued success in the coming years."

Battelle for Kids helps educators and school systems with services, solutions and products designed to advance student-centered learning. it was established in 2001 and works with education organizations in more than 30 states.

News4's David Culver said the board was surprised by the announcement when they were told late Monday afternoon. He said the county will begin an immediate search for an interim superintendent.

Garza recently signed a contract extension for another four years.

Mount Vernon District Supervisor Dan Stork was a member of the county school board when Garza was hired. He pointed to her accomplishments that included a later start time for high school students and abolishing half day Mondays in elementary schools.

"It will be tough to replace her," Stork told News4's Jackie Bensen. "I was very pleased to have hired her. She has done a great job of doing all the things we asked her to do."

Garza was the first female superintendent of Fairfax County Public Schools, the 10th largest in the nation.