This report indicates to principals that their schools probably have a marihuana problem; outlines measures necessary to the establishment of an effective marihuana prevention program; and suggests ways to handle the marihuana smoker once he has been identified. To help the principal focus upon, understand, and take constructive action with respect to the marihuana problem, the report first attempts to educate the large number of high school principals who assume that no marihuana problems exist in their schools. It then outlines the necessary foundations on which the principal and others should construct a program designed to meet the needs of a particular school and community. Finally, the policy formation and its implementation and the role of the principal in a situation involving a student who has been caught with marihuana are dealt with. This last section emphasizes the legal responsibilities of the principal and the various ways in which he can exercise good judgment in the decisionmaking process without forfeiting his legal duties. Appendixes contain texts of federal drug laws; a State-by-State survey of marihuana laws and penalties; and guidelines for establishing a school board policy on drug discovery. (JF)