A humanities teacher at a Massachusetts charter school has been named the 2017 National Teacher of the Year.

The Council of Chief State School Officers announced the honor Thursday for Sydney Chaffee of the Codman Academy Charter Public School in Boston's Dorchester neighborhood. She is believed to be the first teacher at a public charter school to win the national award.

Chaffee teaches ninth-grade humanities at the school, where she has worked since 2007. She also leads the humanities department and manages a partnership between the school and a local theater company.

Her colleagues say she helps students from difficult backgrounds excel in the classroom, and teaches students to work toward social justice.

Chaffee won the state's Teacher of the Year award last May.