SAN FRANCISCO — Several members of the California Supreme Court appeared wary Wednesday of requiring public schools to provide licensed nurses to administer insulin injections and other medications to schoolchildren. The powerful California Nurses Assn. has argued that state law requires licensed nurses to provide insulin injections and other medicines, and two lower courts have agreed. The American Diabetes Assn. appealed. During a hearing, some justices on the state high court appeared skeptical of the nurses' arguments. Justice Ming W. Chin, noting that few schools have full-time nurses, questioned why districts should have to call in a licensed practitioner to administer a shot that a child's parents and physician have agreed could be given by an unlicensed but trained employee.