The proposal would have made class 4A smaller and the remaining classes bigger.
The IHSAA will vote on proposed changes to the state basketball tournament Oct. 2.
Research estimates high school athletes experience between 130,000 and 300,000 concussions every year.
The Indiana High School Athletic Association Board of Directors has approved the new rule.
Non-school sponsored athletic facilities are conducting clinics for students and trying to influence them to attend a school where they are coaching.
A state senator says she may seek a referendum on single-class basketball, despite overwhelming disapproval from players and administrators.
The governing organization for Indiana high school sports issued a report Friday diminishing the hopes for a return to single-class state basketball.
IHSAA has voted to create a sixth class and create a point system for Indiana's football leagues.
Of those attending the town hall meetings, 68 percent favor returning to the original single-class basketball format.
Not since 1997, when Bloomington North won the boys title, has the state held a single basketball tournament for all high schools in the state.