I want to do my photo essay on homelessness. However if I were homeless, I don't know that I would want my picture on someone's homework assignment.
I know where to go (downtown) in my city to find homeless people doing their daily thing -- waiting in lines at the soup kitchen, waiting in lines to get a bed for the night, sitting on the sidewalk panhandling etc... Those are the pictures I want to take (or find on the internet - that is allowed too).
So, if you were taking pictures of someone, would you go up to them, tell them what the project is for, then ask permission to take their picture? Or would you just snap away and assume consent because they are in a public place?