It could be. Hogweed and Angelica are both really large umbellifers, but that does look more like hogweed to me. It likes quite wet soil normally.
It's the sap that does the damage, so if you don't touch them, it's fine. For absolutely obvious reasons, though, they shouldn't be anywhere near a school. My understanding, though, is that you can't force landowners to do anything about them legally (though there may be a very strong moral argument along the lines of 'Imagine how this will play if a child gets burned badly and it emerges that you knew all about the infestation and did nothing'). It's worth getting in touch with the school and the council to see what can be done quickly, ideally before those flowerheads set seed and spread the problem further. (Sadly, funding cuts may be one reason why we are suddenly seeing this story appear).
A bit of awareness-raising in the local community might not go amiss, either. I do think it can be an amazing experience for older children to be taught to recognise very dangerous plants. We can make gardens as safe as you like, but they still will encounter nature at some point, even if they aren't the outdoorsy type. Learning to recognise things like nettles, wild parsley, hogweed, and learning NOT to eat stuff off bushes or any kind of mushroom without a trusted adult's guidance is really important.
Human skin is very sensitive to UV after exposure. If dog skin is the same, your poor friend's pet may need a light summer coat!