The best way to find out who stole $40 from some 7th grader is to traumatically humiliate a bunch of 12-year old girls by having them strip down to their bras and panties and have them shake around until some cash falls out. That fact shouldn't be debated. What needs to be addressed is teaching students about responsibility. If (for whatever unnecessary reason) a middle school student is bringing that much money to school, they need to learn to take better care of it and not put it into a position to be stolen. And when the money is finally found, the teachers should be fired.