Well, it's the last day of the girl's school life and it's an "End of School Life" photo. One for the photo album before life moves on. How many times have most of been called together for a Group Photo and all put our arms round each other's shoulders? It doesn't necessarily mean anything at all. Yes, perhaps the teacher is attached to her. Lots of people get attached to people they spend their working lives with. If he'd had his arm around her shoulder during the educational process I would be a little concerned, but a one-off end-of-term photo in my view, is a rather different affair.