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 Missouri, public school teachers have the right to form and join unions, but they are not covered by the National Labor Relations Act (NLRA) as it applies to private sector employees. Instead, Missouri has its own set of laws governing public sector employees, including teachers. The Missouri Public Sector Labor Law allows public employees to organize and bargain collectively. However, unlike their counterparts in the private sector, Missouri public school teachers are generally prohibited from striking. The state law requires that disputes between public school teachers' unions and school districts be resolved through negotiation and, if necessary, mediation or arbitration. While teachers' unions in Missouri can negotiate contracts covering wages, hours, and other terms and conditions of employment, they must do so within the framework of state laws that govern public employment.