1. The Excitement Level
In your senior year of high school, all you can think about is how great it's going to be to finally get out of high school and move onto the fantastically fun world of college. Of course, after 13 years of pre-college education, it's an honor and a privilege to be so excited, but if only you had known what could come next you might have cried instead of laughing. College rolls around and by the time you're a senior you've endured a whole new journey full of being broke, working too much--academically or otherwise--and the world you're about to enter has no sense of certainty (unless you're very lucky) due to your lack of direction while seeking a new job in a new location ASAP post-graduation. Although you've come so far, you have so far left to go before your post-grad life reaches its full potential, and that can be extremely exciting...but it's mostly scary.
2. The Garb
Some students in high school wear uniforms, but others just have a ridiculous dress code to abide by, but either way your choice of dress is not truly yours. It can be mind boggling to think you've work basically the same outfit for four or more years and although you might have a closet full of clothes, you might have some trouble picking out outfits in the short time you set aside to get ready once you arrive at college. Thankfully, college has little to no dress code, although "professional" dress may be required for some presentations, on a daily basis you're welcome to dress up or dress down, ranging from pajamas to suits and everywhere in between. You'll learn a lot about people just from how they dress once you get to college, and thankfully most people don't care if you're on trend; college is more about comfort than conformity.
3. The Community
In high school you probably knew everyone, or at least most of the people in your grade, and it makes socializing come much more naturally. By your senior year of high school you probably have a set group of friends who have been with you through thick and thin. It's bittersweet to be parting ways with them, but it'll give you tons of places to spend your weekends when you visit all your friends both near and far. However, in college, friends come and go. Depending on the program's you're involved in, what major you've chosen, how often you work, and where you live, your group of friends will grow and change throughout your four years. During senior year people get extremely busy trying to bust out those last few papers, exams, presentations, and internships. However, the people who truly matter will find ways to spend time with you or at least keep up communications. Although high school led to a grand new adventure, college leads to one that may take you far away from all your friends with a very reduced chance you'll be able to visit. Take advantage of living down the hall or down the street from your best friends.
4. The Financial Sitch
In high school, you got to live with your parents and they paid your way throughout your academic career for field trips, activities, t-shirts, class trips, sports, band, choir, and any other fun extracirriculars that cost money and would help you get into college. In college, the cost of the classes alone can bankrupt you, much less participating in anything outside of academics. You may have had a job in high school, but that extra spending money is suddenly funneled into the fund for rent, bills, food, gas, and all the other fun fuel it takes to make it at college. You might be lucky and get some help from financial or parental aid, but in the long run this is the beginning of the end of being taken care of financially. As our parents would say "welcome to the real world!"
5. The Classes
In high school, the idea was to sufficiently prepare you for the next step of your life, whether it be college, heading out into the working world, joining the armed forces, or any unforeseen future you're headed toward. Basic knowledge learned by all means that everyone in your grade can study with you and help you complete assignments or projects. In college, you'll ideally be prepared to head out into the world armed with your college education and the ability to exercise your strengths to get a professional position. Honestly, you'll be lucky if you know anyone in your classes, even by senior year. The group of people in your major may change so much over time that you don't recognize many faces, and sometimes you won't take classes at the same time as them and you'll recognize no one. The great thing is you probably know people who graduated who passed down notes and study materials to get you through. This is tradition, so don't forget to pay it forward and forge on to the moment you're holding your degree and ready to conquer the job market.