Twelve Hamilton County teachers from a variety of disciplines earned National Board certification in December, according to a news release.

The certification is awarded by the National Board of Professional Teaching Standards and is the highest credential in the teaching profession. It requires a rigorous, performance-based assessment that typically takes one to three years to complete and measures what accomplished teachers should know and be able to do, the release states.

Teachers must build portfolios that include student work samples, assignments, videotapes and a thorough analysis of their classroom teaching. They also are assessed on their knowledge of the subjects they teach.

Hamilton County has established a support system for certification candidates through the schools system, the county education association and the Chattanooga Area Schools Federal Credit Union with funds from Race to the Top and the National Education Association Foundation.