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 Illinois, teachers' unions are recognized and have the right to engage in collective bargaining on behalf of their members. This includes negotiations over salaries, benefits, working conditions, and other terms of employment. The National Labor Relations Act (NLRA) of 1935, which provides for the rights of workers to form unions and engage in collective bargaining, does not apply to public sector employees, including public school teachers. However, Illinois has its own set of laws that govern collective bargaining for public employees. The Illinois Educational Labor Relations Act (IELRA) specifically addresses the rights and obligations of educational employees, including the right to organize and bargain collectively through representatives of their own choosing. The IELRA also outlines the process for collective bargaining and sets forth the legal framework within which teachers' unions operate in the state. Unlike some states that prohibit collective bargaining or strikes by public employees, Illinois permits these activities within the education sector.