I explored Instagram for this post. I found its features easy to use and the search seems similar to Pinterest. I discovered quite a few friends who already use the service, so it was easy to find people to follow. Today when I checked, I am being followed by two people. :-)
All that said, I see these friends photos on Facebook for the most part. Some through Google+. I can set Instagram to post to Facebook, twiter and other services automatically, too. I was disapointed that the app is designed for phones, though it can be used on the iPad. The format is portrait only, so my iPad doesn't stand up on it's own for viewing. I would think that more people are usign this app on their phones, though. It would be much easier to document events with a phone camera rather than an iPad. There is a nice set of photo options on Instagram, too. I don't tend to like to edit my photos, but it is nice that they are there and easy to use. Just a swipe of a finger and a tap on an icon to get to them.
I confess that I probably won't use this app much on my iPad. I'm not sure how I would promote it to staff and students at school either. We would need to keep all the pictures private. This is possible, though and could be a way for teachers to share pictures to just the families of their students. I am not sure what today's parents would prefer.