The following is taken directly from the California Interscholastic Federation Constitution & Bylaws 2013-14:
By Laws Article 190
By Law 1908 MERCY RULE
At the conclusion of the third quarter or any point thereafter, if there is a point differential of 35 or more points, a running clock shall be instituted for the remainder of the game regardless of the score. The game clock shall stop only for a score, a free kick following a fair catch or awarded fair catch, a charged team timeout, a coach-referee conference or an official’s timeout. This bylaw applies to all levels of play.
(approved May 2011 Federated Council)