Requires such a law to require that: (1) any public or private school administrator or employee with reasonable cause to believe that a student is or has been in possession of a firearm while in or on the premises of a school building in violation of Federal or State law immediately report the student's conduct to an appropriate law enforcement agency and juvenile department or State agency; (2) upon receipt of such report, the law enforcement agency immediately investigate whether there is probable cause to believe that the student possessed a firearm in violation of Federal or State law; (3) if probable cause is determined, the student immediately be detained by the law enforcement agency (with notification to parent or guardian) for up to 72 hours in an appropriate juvenile justice setting for psychological evaluation and a judicial determination of whether the student is a danger to himself or herself or to others; and (4) if the court determines that the student is a danger, the student be placed in an appropriate juvenile justice setting to receive professional psychological counseling.