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 Indiana, teachers' unions operate within the context of state laws that govern public sector unions, as the National Labor Relations Act (NLRA) does not apply to public school teachers. Indiana does not prohibit collective bargaining for public employees, including teachers, which means that teachers' unions can negotiate with school districts on behalf of their members for matters such as salaries, benefits, and working conditions. However, Indiana Code Title 20, which covers education and cultural affairs, includes specific provisions that limit the scope of collective bargaining for teachers to salary and wage-related benefits, excluding issues like class size or curriculum. Additionally, while Indiana does not have a statute that explicitly prohibits strikes by public employees, such actions are generally considered illegal based on state precedent and could lead to penalties for participating teachers and unions. It's important for teachers and unions to consult with an attorney to understand the current legal landscape and their rights under Indiana law.