hi bro, the thing is that the classical approach is a bigger concept regarding humans as machines. it believes that human beings are rational in their decision making. scientific management, bureaucratic management and the administrative management are the parts of classical approach. the scientific management approach advocates one best way and all.. the bureaucratic approach headed by weber advocates the need for strong institutions for achieving efficiency and the administrative management believed in efficiency but the seeds for the human relations or the humanistic approach were sown by the adherents of this approach, like the acceptance of the fact that there are informal organizations within the formal organizations and the acceptance theory of authority by Chester Barnard.
I hope that u got the answer u were looking forward.