Legal Question in Business Law in California

Perhaps. The question would be whether the school was negligent in requiring this kind of policy regarding locking, and in allowing someone to obtain and use a master key to steal property. Sounds from the facts given that the affected students would have a reasonably good case, but it's not a slam dunk that they'd win. Also, there are special rules regarding lawsuits against public agencies and the government, and I'm assuming this is a public school; the students or their parents would need to comply with these claim-presentation and case-filing rules in order to get their claims before a court. I think the students or teir parents, or a group of them, might want to consult a local lawyer and also try to negotiate with the school administration before making a formal claim to be followed up with a lawsuit, which could be expensive.