Another comment I want to add (aimed especially at elementary lady teachers!) is to pay (significantly) more attention to preparing well for your procedures and lessons layout than to decorating the room. I intentionally keep the walls pretty simple for the first days and then strategically add more things as the days go by. Too much glitz can both give the wrong message and over-stimulate young minds. Putting up new things little by little enables students to notice specific items more. I often ask, “Did you see anything new today?” and then we talk about the new thing and its purpose.