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 Pennsylvania (PA), teachers' unions operate under state-specific regulations, as the National Labor Relations Act (NLRA) does not apply to public sector employees, including public school teachers. Pennsylvania allows collective bargaining for public employees, including teachers. The Pennsylvania Public Employee Relations Act (PERA) governs labor relations between public school districts and their employees. Under PERA, teachers have the right to organize, join unions, and engage in collective bargaining over terms and conditions of employment. The law also sets out the procedures for collective bargaining and resolving disputes, which may include mediation and arbitration. However, while teachers in PA have the right to collective bargaining, they are generally prohibited from striking, especially if the strike would endanger the health, safety, or welfare of the public. The Pennsylvania Labor Relations Board (PLRB) oversees and enforces these regulations. It's important for teachers and school districts to consult with an attorney to understand the specific applications of these laws.