A teachers’ union is a labor union (an organized group of employees) that represents teachers or educators in contract negotiations (for salaries, tenure, paid time off, and other terms of employment) with schools or school districts. Teachers’ unions are said to engage in collective bargaining—bargaining or negotiating on behalf of all teachers—rather than individual teachers negotiating their own employment terms.

The rights of workers to form unions, strike, bargain collectively, and engage in other work-related activities are provided by the federal statute known as the National Labor Relations Act of 1935 (NLRA). The NLRA also prohibits unions from trying to force workers to join a union and prohibits employers from retaliating against workers who exercise their union rights.

The NLRA supersedes many state laws but it does not apply to employees in the public sector—including public school teachers. Some states have laws that prohibit collective bargaining for public employees (Georgia, North Carolina, South Carolina, Texas, Virginia) and many states have laws that make it illegal for public employees to strike.

In California, teachers' unions are recognized and have the right to engage in collective bargaining on behalf of their members. This includes negotiating contracts that cover wages, benefits, working conditions, and other aspects of employment. California's public sector employees, including public school teachers, are governed by state laws rather than the National Labor Relations Act (NLRA), which does not apply to public sector employees. Specifically, the California Educational Employment Relations Act (EERA) of 1976 extends collective bargaining rights to public school teachers and other educational employees in the state. The EERA is administered by the Public Employment Relations Board (PERB), which oversees the collective bargaining process, resolves disputes, and ensures that both unions and school districts adhere to the law. Unlike some states, California does not prohibit public employees from striking, but there are legal processes and restrictions that must be followed before a strike can occur. Overall, California is considered to be a state supportive of collective bargaining rights for public school teachers.