Escalating the conflict over the teaching of race, the American Federation of Teachers’ New Hampshire affiliate filed a lawsuit Monday charging that the state’s new law, restricting certain lessons, is unconstitutionally vague and an abridgment of free speech.

The New Hampshire law, signed over the summer, bans public schools from teaching that one’s race, sex or other characteristics are “inherently superior” to others, or that people are inherently racist, sexist or oppressive on account of their race, sex or other characteristics.