First, in the future please resize your images. Those would have sucked on broadband, and a number of us are restricted dial up due to our location. A 2.2MB image is just painful. PM if you aren't sure how to do that. (Also, fileup is a painfully bandwidth issues- photobucket or imageshack will give you better performance even on these beasts.) I'm not busting your chops, I'm just saying that grabbing those images hurt and they didn't have to.

Have you looked for the school's plan yet? My suggestion would be less water, and possibly pull some stuff out of the FAK. It is a great kit, I've build off several of them, but there is some unneeded bulk like the empty pill bottles if you haven't cracked it yet. (Bulk out = space found! And you probably already have a triangular bandage in there if it was packed to spec when you bought it.)

There are two reasons for me saying that. One is becuase your school has a stock of supplies. Being able to get off those is great, but as a student under their care you aren't able to leave so you might as well sit tight.

Two gallons of water is great, but it is a LOT of water for your pack. Is the Jansport your normal book bag? Maybe a new backpack that has side pockets, and two quart bottles in those, refilled as needed during the day would make sense. That would also let you escape the quandary you posted- how do you get to this if you locker isn't there any more. It turns it into an EDCed kit if you move some items to the FAK once you've cleaned it out some, it won't take up much space in your pack.

Other thoughts, now that I've seen it.
-Chemlights do suck. Maybe one. Maybe. Not an issue if in your locker, is a volume issue in a backpack.
-Craft stores and some hardware stores sell small zipper bags, 2x2. Yes, they look like paraphernalia when empty- that is why you pack a pair of nitriles into each one. Turns into a wrinkly, solid, blue rubbery thingy that most people can't ID, but it isn't drugs. :P But it also keeps them under control. Same thing for the earplugs that were mentioned, and your batteries.
-Better garabage bags. General around the house bags are usually pretty light, and often have been treated with something. Look for a leaf bag or a contractor's bag- it is bigger, doesn't take up any more room, is more robust and won't make you sick if you have to use it as a poncho.
-Again, go through the FAK. If it is the same one I use for my start, you've got some stuff you can pull to make room.

And if that was all that was in that backpack... I own one. You need to learn to pack. :P But if you can get it into your EDC pack, and stash the big water in your locker, you're good even if you can't get to the locker.