Illinois High School Boys Basketball Championship

The Illinois High School Boys Basketball Championship is a single elimination tournament held each spring in the United States. It is organized by the Illinois High School Association (IHSA).

From 1908 to 1971, it was a single tournament contested by nearly all high schools in Illinois. In 1972, the tournament was divided into two divisions based on school size, (A and AA), each producing a separate champion. In 2008, the tournament was divided into four separate divisions (1A, 2A, 3A, and 4A being the larger schools). The Illinois High School Basketball Championship was the first tournament to be called 'March Madness'. The term was first used about the Illinois tournament in 1939, decades before it was used about NCAA basketball tournament.

Under the current four class system, teams are assigned to a class, based on the student population, with adjustments made for single gender schools, and for schools which are not four year high schools. Within the class, schools are geographically assigned to a regional, which is, in turn assigned to a sectional which, finally, is assigned to a super-sectional. Regional tournaments are generally between four and eight teams, depending on the number of teams in a geographic area in a particular class. There are four regional tournaments within each sectional and two sectionals within each super-sectional. Each tournament is single elimination.

Within the regional, coaches seed the teams. The winners of the four regional tournaments then meet in a single elimination sectional tournament. The teams are not re-seeded after regional play, and the winners of the regional tournament are randomly assigned, in advance, to play the winner of one of the other regionals in the sectional semifinals.

For example, in 2011, in the Class 2A Casey Sectional, there were four regionals: Flora, Monticello, St. Joseph and Robinson. Three of these regionals consisted of five teams and one of six. Before the playoffs began, the IHSA assigned the winner of the Flora Regional (which ended up being Teutopolis) to play the winner of the Monticello Regional (Champaign St. Thomas). The winners of the St. Joseph and Robinson regionals played in the other regional semifinal, with the winners of the two semifinals met in the sectional championship.

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