Traditionally, most students had them taken before school started for their senior year. This was to make sure the photographers could get the images ready for the yearbook deadline in September. Most schools now contract a photographer to schedule these yearbook/formal photos one or two days during the summer. This works great for the schools, but not always as personal as you might want for your special photo session. Just because you are required to use the school photographer for the yearbook photo, that does not mean you cannot choose another photographer for your personal
session.
Are you going to be super busy after school starts? This applies to a lot of athletes that have practice after school everyday, games that run late into the night. Also football gear can sometimes cause more breakouts to the skin. If you have college classes or AP classes you might not have much flexibility to leaves school for a photo session. If you are working, it might be harder to take off work for a photo session. In these cases, summer before school starts is definitely a better choice.
If you are wanting outdoor photos with nice green trees and grass, it is better to have them done before mid October. Wildflowers are blooming like crazy in the fields at Hardgrave Photography during the last part of September - first part of October. Even now in July, we have lots of wildflowers.
If you are wanting "fall colors" you need to plan very carefully. In our area, the colors usually do not change till the first week of November, and they are for a limited time! Also by they time the leaves change, daylight savings time has changed and our outdoor times are much shorter - you will need to plan on taking time from school.
Keep the holidays and "senior" expenses in mind. Usually you will order your photos about a week after your photo session. After school starts, you will have homecomings, and depending on your school, other dances -some formal, others not. Traditionally, you will order cap & gown, senior trinkets, and invitations around the first part of November.
Your "Senior Page" in the yearbook has a deadline too, usually before the Christmas break (check with your yearbook advisor). This is the page you can use some of your digital images from your professional session along with images from your childhood.
If you want snow pictures... it is almost impossible to predict a snow day in Arkansas, and you probably don't want all of you images in the snow - so if you have your session taken before then, and want snow photos, I will give you a free mini session with discount on purchased prints from the snow session. You just have to be able to get here!
If you are thinking about spring photos - just be aware that it really does not get pretty outside until April, which puts you close to graduation.
If you only want indoor photos, then you don't even have to worry about the weather, only about when the timing is best for you.
I hope this helps you decide, no matter which photographer you use.