Here are the 2015 NFHS rule changes, as posted by the MSHSL:
SPEARING DEFINITION REVISED (2-20-1c): Continuing the focus of risk minimization, the definition for the illegal helmet contact act of spearing was revised. Spearing is an act by any player who initiates contact against an opponent at the shoulders or below with the crown (top portion) of his/her helmet.
CORRECTING A DOWN NUMBER ADDED (5-1-1b NEW): The referee is granted authorization to correct the number of the next down before a new series of downs is awarded.
FREE-KICK FORMATIONS REVISED (6-1-3; 6-1-4 NEW; 6-1 PENALTY): In a revision of the 2014 rule change regarding free-kick formations, the timing of the foul for not having at least four players on each side of the kicker now occurs when the ball is kicked.
EXCESSIVE CONTACT ADDED TO UNNECESSARY ROUGHNESS (9-4-3g): With an emphasis on risk minimization, the unnecessary roughness provisions were expanded. No player or nonplayer shall make any other contact with an opponent, including a defenseless player, which is deemed unnecessary or excessive and which incites roughness.
ROUGHING THE PASSER PENALTY CLARIFIED (9-4 PENALTY): An automatic first down is not awarded for a 5-yard incidental face mask penalty against the passer.
DEAD-BALL PENALTY ENFORCEMENT MODIFIED (10-2-5): The distance penalty for unsportsmanlike, nonplayer or dead-ball personal fouls committed by teams can offset. Equal numbers of 15-yard penalties by both teams will cancel and remaining penalties may be enforced.