SAN FRANCISCO — California schools may give students insulin injections and other medications without having to call in licensed nurses, the state's highest court ruled Monday. "California law expressly permits trained, unlicensed school personnel to administer prescription medications such as insulin in accordance with the written statements of a student's treating physician and parents," Justice Kathryn Mickle Werdegar wrote for the California Supreme Court. The unanimous decision was a defeat for the powerful California Nurses Assn., which had argued that only licensed healthcare workers could administer medicine under a state law that bars the unauthorized practice of nursing.