It is understand some class photographs were taken before the pupils with additional support needs were brought in.
How did that happen, when no one in the school was in with it? Where were the kids with complex needs at that time? As a parent I would have a closer look at the school, no matter what they say now. I mean it takes time to get the kids stand together, stop making funny faces etc. This was not done in five minutes or the pictures would be awful.
I'd imagine (from personal experience): the period before was split, with one part of the class doing something and the others doing something else. Therefore they didnt arrive at the photoshoot together.