No, that is not the way it works EVER. You don't understand the process. People have a right to due process. You can't fire a person just because a cop comes and says that person is under investigation for something. The first step is always to document it. The second step is to investigate it. The third step is to fulfill legal requirements, such as giving the employee their paycheck, and proper written notice of the reason they are being fired. That's the law. The school does not have a right to violate the teachers rights, no matter what he may have done.
Respectfully, I work closely with schools regarding abuse or contact with minors. Teachers in his position can and are fired immediately upon indiscretion, or at the discretion of the firing party...which can vary by district. A teacher in his position can absolutely be told one day not to come back the next. (I say his position, because the process with a tenured teacher or elected position is different. Because he is not a certified teacher, the protections he is afforded by a union or board is not the same. He's basically a "guest teacher" for lack of better words.)