When do you have to get your Senior Pictures taken by?

Okay, so I'm going to be a Senior this year, and I have to get my senior pictures taken. I think I'm going to get them done by Bob Dicaprio. My first day of school is August 31st. I want to know when do I have to get the pictures taken by? Do I have to get them done BEFORE the first day of school? Or can I get them done AFTER the first day of school, in the first couple weeks? All answers are apprciated! Thank you sooooo much!(: