All local and regional boards of education and all private elementary and secondary schools may authorize the search by school or law enforcement officials of lockers and other school property available for use by students for the presence of weapons, contraband or the fruits of a crime if (1) the search is justified at its inception and (2) the search as actually conducted is reasonably related in scope to the circumstances which justified the interference in the first place. A search is justified at its inception when there are reasonable grounds for suspecting that the search will turn up evidence that the student has violated or is violating either the law or the rules of the school. A search is reasonably related in scope when the measures adopted are reasonably related to the objectives of the search and not excessively intrusive in light of the age and sex of the student and the nature of the infraction.