The board of supervisors may provide financial assistance to elementary school districts which have within the boundaries of such school districts (a) a redevelopment agency and a housing authority organized under state law, or (b) any facilities used by the county to house county employees. Any funds received pursuant hereto by an elementary school district may be deposited by the governing board of the school district in any fund of the district. The provisions hereof are applicable only to elementary school districts which have an average daily attendance of less than 3,000.