Cal. Educ. Code § 17921

A school district or county office of education that establishes a schoolbus emissions reduction fund may receive revenues from air pollution control district and air quality management district grants, revenues from a city that are granted pursuant to paragraph (1) of subdivision (b) of Section 44243 of the Health and Safety Code, or from any other source. The school district or county office of education shall contribute a majority of the money deposited in its schoolbus emissions reduction fund.