It doesn't need to be a large one, they won't have much storage room. Grab an extra backpack while they are on sale and put the stuff in there. It can be tucked under a bed, in the corner of a closet out of the way. I like a bright red one or neon bright one so it's easy to see in the dark if necessary.
If you do an internet search of supplies for a 72 hour kit, you will get inundated with huge lists that may overwhelm you at first. Don't let it! Here's a simple idea from emergencypreparednessandresponse that'll feel alot less overwhelming and easier to put together during the busy weeks ahead:
List One is the simple essentials. Get them for sure, and then add items from List Two if you desire to add extra.
1) Buy if time is an issue: Don't have time to make one and throw it together? Go ahead and buy one! Do a google search for 72 hour kits and thousands of options will come up for you. The peace of mind for you as a parent is priceless!
2) Water Storage: One gallon per person per day means you need to store 3 gallons of water somewhere in his/her dorm room. Propping her bed up with simple wooden blocks and storing them under her bed on their sides is one option. Another one is to buy 4 gallons, place them in each corner of her closet floor and then lay a 1 x 8 inch board (or whatever size you want/will fit) across the tops of them for an extra shelf space!(Bam! Shoe organizer right there!) A local big box hard ware store can make the cut for you to the needed length of the board (usually a free service) and you have a discreet way of storing the water.
3) Food Choices: Let's make this easy. They may be asked to stay put in their dorms/apartments for awhile on lock down or whatever. It could be with no power, so make it easy on the food choices. Items like pouches of tuna or chicken, can's of ravioli, etc. can be eaten without heating if necessary. Protein bars (rather than regular granola bars) will give them some added nutrition they will need during this stressful time. And throw in some treats like cookies, hard candies etc. (throw a can opener in to the pack or make sure to buy all pop tops/tear open pouches!)
4) Evacuation in flip flops?: Ok so I'm a mom and realize that most kids in the middle of the night or anytime really if they need to evacuate quickly are gonna grap their flip flops and go. Not a great idea for having to manage who knows how much walking, climbing, or whatever. SO, even though your child will think you are completely ridiculous (hey that really isn't a new thing, though right?) do the following (courtesy of emergency preparedness and response): Take an old pair of their tennis shoes. Tuck a pair of socks into the toe of one shoe. Also, place a flashlight into one shoe and a whistle into the other. The flashlight, well that's for obvious reasons, the whistle is so they can be heard if they are trapped. Now, take some duct tape and tape them somewhere to the underside of their bed frame. This way they won't get lost in a slightly messy room and are easy to grab and go. NO EVACUATIONS IN FLIPPY FLOPS!