Searches of students in school has long been a contentious issue, as exceptions to the Fourth Amendment probable cause warrant standard have permitted school personnel to use a lower standard. FourthAmendment.com notes this case in Washington, where a court held that if a school resource officer (SRO) was acting as a police officer, the exception does not apply:
A school resource officer was acting as a police officer enforcing the law when he arrested defendant in the boys bathroom holding a bag of marijuana. A search incident of his backpack was otherwise unreasonable under Washington law, and it was suppressed. State v. Meneese, 2012 Wash. LEXIS 540 (August 2, 2012) (dissent).*