I also go to school and I take with me different things. I have a little tupperware box that I pack stuff in...you can also get a small lunchbag that lets things stay cool that fits in your bag. I take with me seasonal fruit, trail mix, crackers with PB or pretzles with PB, and almost always hummus with fresh veggies. my favorites are lemon cilantro hummus with cucumber, cherry tomatoes, green beans and apples. It may sound weird but the sweet of the apples with the savory hummus is soooo good. Also, I take with me soybeans in their pods, great snack.
and i'm not quite vegan so occasionally i take hard boiled eggs...but eat those outside else they will stink up the room. :-)
Get yourself a little tupperware container that are small, mine has little compartments in it. this way you can take a couple of things with you. also, make some stuff the night before like a barley salad or a couscous salad with fresh veggies, beans, herbs and citrus dressing. that doesn't need to be refrigerated but you can put a little ice pack in your lunch bag and keep it cool.
Every morning, I prepare a green smoothie in my 2HP VitaMix blender. It consists of kale, lemon, orange, other fruit, carrots, ice, and pure well water. I carry the smoothie in a quart canning jar with a sealing lid.
The fiber in the smoothie carries me through for several hours.
Trail mix...make sure there are some nuts in the mix, the fats will help keep you satisfied. Cut up veggies w/peanut butter already on them. Energy or protein bar w/a piece of fruit. Some sliced or chunks of baked tofu...I'm in love w/the Wildwoods Royal Thai flavored one., that with cut up veg's. Whole Foods use to sell soy jerky, soooo good, this along with some cut up veggies.
I second the pb sandwhich-- I add banana to mine sometimes too. Also Tahini is amazing-- some plain organic sesame paste with avocado and tomato and lettuce, or eve just the Tahini plain! Filling and easy! If you are new to tahini, try the light version (it's not 'light' in terms of calories, it has to do with whether the husks are ground into the paste!).
If that's not filling enough, you can always add some tempeh to the sandwich.