Definitely a backpack.
I have been using Dakine backpacks for years. They are extremely durable and one of the most comfortable backpacks I have owned. My friends claim that my backpack is invincible. ;D I went with Dakine because of the sole purpose of them having packs made to carry boards, which is a necessity for me. Most of their packs might be far too much than what you would need, but if I am not mistaken they have basic models that would be great for school.
Messenger bags put too much pressure on one shoulder instead of evening out the weight on both shoulders. A lot of people I know have ended up with neck problems when hauling around heavy things in a messenger. Just a thought to consider. :-)
Good luck!
Edit/ Forgot to add that most models have fleece-lined pockets made especially for cameras. That might come in handy with some of your photography stuff.
The Minions:
{The Dog: Towser & Raiden} {The Cats: Khaith, Martha, Adelaide, Snowball, & Floki} {The Bird: Gir}
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