California Code, Education Code - EDC § 48901.5

(a) The governing board of each school district, or its designee, may regulate the possession or use of any electronic signaling device that operates through the transmission or receipt of radio waves, including, but not limited to, paging and signaling equipment, by pupils of the school district while the pupils are on campus, while attending school-sponsored activities, or while under the supervision and control of school district employees.

(b) No pupil shall be prohibited from possessing or using an electronic signaling device that is determined by a licensed physician and surgeon to be essential for the health of the pupil and use of which is limited to purposes related to the health of the pupil.