searches by security guards
My sons school does regular drug searches using a security company who makes use of narcotics dogs, in there last search the started conducting random physical searches of the students most of which were minors. They were searched in front of the entire school without being informed why they were being searched or asked if they give consent to be searched. There were no saps present at the search. There was no warrant obtained. Even the female students were searched in the same manner just with a female guard.
Unless there is the presence of a strong reasonable suspicion, I do not think it is within the rights of the school to bring in private security to conduct random searches on the body and/or lockers of the students without their consents being obtained. I will however advise you address this further with the department of basic education.