To maintain reduced class sizes, purchase textbooks and teaching materials; enhance core subjects; attract and retain teachers; maintain library services, counselors, after-school programs and custodial services; and fund school safety programs, shall West Contra Costa Unified School District be authorized to levy, for 8 years commencing upon the expiration date of the existing parcel tax, an annual tax of 11¢ per square foot of total building area or $11.00 per vacant parcel, with an exemption for eligible senior citizens?