I normally prepare my children for their elementary school picture.
I usually put gel in my son's hair and style it, so that it won't move. For my daughter, I usually blow out her hair and style it straight with the flatiron.
I then spray her hair with hairspray so that it won't move. I usually take both my kids to get their hair trimmed a week before the pictures are going to be taken.
This way the hair is neat and all I have to do is style it. It is harder to style hair when they hair style is overgrown.
I usually order school pictures on the first day of receiving the envelope. The school picture prices go up every year, but you really have to buy the pictures.