Substitutes should arrive at least 15 minutes before the start of the school day. Why? Because your demeanor when the students enter your classroom will set the tone for the rest of the day. If you are running late, unprepared, and frantic, the rest of your day will likely be unorganized and frantic. So, give yourself plenty of time to park, sign in, pick up materials, and go over lesson plans and you will feel much more confident and prepared going into your day – and your attitude will rub off on your students!