Section 2. The department shall provide a comprehensive and coordinated program of delinquency prevention and services to delinquent children and youth referred or committed to the department by the courts; community services for the prevention of juvenile delinquency through its own staff, through grants-in-aid to cities, towns, and other public agencies and through purchase of services from private nonprofit agencies; and services and facilities for the study, diagnosis, care, treatment, including physical and mental health and social services, education, training and rehabilitation of all children and youth referred or committed. The department shall maintain a program of research into the causes, treatment and prevention of juvenile delinquency, including new methods of service and treatment. The department shall cooperate with other state and local agencies, both public and private, serving children and youth.