In CA, it's legal to carry in a GFSZ/on school property with a valid CA CCW permit.
Penal Code 626.9
(a) This section shall be known, and may be cited, as the Gun-Free School Zone Act of 1995.
(b) Any person who possesses a firearm in a place that the person knows, or reasonably should know, is a school zone, as defined in paragraph (1) of subdivision (e), unless it is with the written permission of the school district superintendent, his or her designee, or equivalent school authority, shall be punished as specified in subdivision (f).
(l) This section does not apply to a duly appointed peace officer as defined in Chapter 4.5 (commencing with Section 830) of Title 3 of Part 2, a full-time paid peace officer of another state or the federal government who is carrying out official duties while in California, any person summoned by any of these officers to assist in making arrests or preserving the peace while he or she is actually engaged in assisting the officer, a member of the military forces of his state or of the United States who is engaged in the performance of his or her duties, a person holding a valid license to carry the firearm pursuant to Article 3 (commencing with Section 12050) of Chapter 1 of Title 2 of Part 4, or an armored vehicle guard, engaged in the performance of his or her duties, as defined in subdivision (e) of Section 7521 of the Business and Professions Code.