Which basketball rules can my state association change?

Each state association adopts the NFHS rules and can modify them. Options the NFHS rules book itself leaves to the state include:

• Shot clock: a state may adopt a 35-second shot clock. Without state adoption, there is no shot clock.
• Closely guarded: a state that uses the 35-second shot clock may eliminate the five-second closely guarded count while a player is dribbling (Rule 9-10-1a Note). The five-second count for a player holding the ball still applies everywhere.
• Coaching box: the size is a state option, up to a maximum of 28 feet.
• Who clears a concussed player: the state decides who counts as an "appropriate health care professional."

States also set things outside the playing rules, such as ejection reporting, suspensions and officials' registration. If your state publishes its own modifications for the season, they override the NFHS default for games in that state.