In the United States, the major forms are high school football, college football and professional football. Most American high schools field football teams. In general, high school teams play only against other teams within the same state, but there are some exceptions like nearby schools located on opposite sides of a state line.
Most of college football in the United States is governed by the National Collegiate Athletic Association (NCAA), and most colleges and universities around the country have football teams. These teams mostly play other similarly sized schools, through the NCAA's divisional system, which divides the schools into four divisions: Division I Bowl Subdivision, Division I Championship Subdivision, Division II, and Division III. Unlike the three smaller NCAA football divisions, the Division I Bowl Subdivision does not have an organized tournament to determine its national champion. Instead, teams are invited to compete in a number of post-season bowl games. In addition, the champions of six conferences in the Division I Bowl Subdivision receive automatic bids, and four other schools receive "at-large" bids, to those five bowl games under the highly lucrative Bowl Championship Series to help determine the national champion.
The highest level major professional league in the United States is the 32-team National Football League (NFL). Another professional league, the 5-team United Football League, also currently operates. Several semi-professional, women's semi-professional football, and indoor football leagues are also played across the country.