For me, it was probably how hard the work can actually be. I was seen as “gifted” by my peers my whole life, but in reality all the work during my earlier years were piss easy. Since high school actually provides challenge with schoolwork and generally figuring out who you truly are, it’s all been somewhat of a pain in the ass to deal with.
I pretty much coasted through school until I graduated from high school. College was a whole different level and I didn’t expect that and didn’t adjust to it. Up through high school, teachers are pushing you to learn and succeed. But in college, the principle essentially becomes “We will offer you the opportunity to learn. But it’s up to you to do the work. We’re willing to let you fail if you don’t keep up.”
College was also a major change in lifestyle. I imagine I was like most people through high school; I lived at home and my parents provided for all of my basic necessities. College was the first time I was living independently and had to do things for myself.
For me, it was learning that others that found high school easy would find college difficult. I went to the same school as a number of high school classmates, including one of the valedictorians. But he struggled in calculus and physics and some engineering classes whereas I did not. It’s not that I found college easy, exactly–but it was finally interesting and that motivated me. High school stressed me out greatly due to the immense amount of busywork, which I could not be arsed to do most of the time. College lessened that. For the most part, the harder the class the better grade I got.
For me: how screwed you would be if you ended up with a horror of a teacher for any subject in 7th through 12th grades and also at university.
What pleasently surprised me about going to university was the lack of the high school cliques. People seemed to have more purpose and also to be more invested in said purpose. I did start my university career as a “space available” student on a military base, but I observed this phenomenon then, and also when I returned to university after retiring from the military.
Nothing hit me hard in these transitions. Life kept getting nicer and more pleasant and more interesting. In retrospect I think that was because my life in my family home was pretty creepy and awful, and I moved out shortly after turning 16 and things became so much better.
If there was a big surprise, it was that I could live away from my mother’s house so easily and with so little trouble. It was a breeze!
Beer. Free beer at fraternity parties. Oceans of it. Thursday pub nights, Friday happy hours, Friday and Saturday night open parties. Definitely cost me a bit off the GPA.
And that nice briefcase I got as a high school graduation present? Just leave it at home. Get the backpack.
It was the greatest thing to happen to me in my whole life.
NO BULLYING!
I grew four inches that year. It was heaven!
High school was better than middle school, and college, even with its bumps and disappointments, was heaven. Adulthood! I enjoy it.
For me, the biggest adjustment when I got to college was that I was in charge of my own education.
Through grammar and middle school, there were basically no decisions for the student to make. In high school, sure, there were a few electives and some choices to make, like sciences and languages - but you pretty much got on a path and followed it.
So when I started college, I was not at all prepared. I attribute this partly to the failure of my sub-par high school counselor to do much of anything to let me know what to expect, and partly to my own naïveté and, frankly, laziness. I drifted through five semesters without even declaring a major. Nobody was there to tell me what to do and I didn’t bother trying to figure it out for myself or seek guidance, so my college years were totally aimless and wasted, until I just quit.
I did go back and finish my bachelors some years later, but if I had it to do over again I would be much more active at taking control of my own destiny.
The hardest thing for me the girls were uglier and less friendly in college. It took me several years to lower my standards enough to get laid on a regular basis. That probably had more to do with growing up on the beach in California and then moving to an inland engineering school.
Aside from that school was basically the same as high school go to class then go to practice then go home and do homework pass out and repeat. I picked a major which was basically the only decision I had to make with regards to my education they picked out 19 credit hours a semester for me to graduate in 4 years and I got three electives to choose over 4 years.
Fat, drunk, and stupid is no way to go through life.
The amount of work needed to be even minimally productive as a college student was way beyond anything I experienced in high school, where I had a 3.95 GPA and was only a single letter grade short of salutatorian.
Ultimately, I failed to adapt and flunked out of college my first term of sophomore year with a 0.5 GPA that term (1.5 overall). The day I realized I wouldn’t graduate was the most emotionally devastating day of my life. I spent like half an hour just sobbing in an empty field. Good times.
After 13 years of just working and not really achieving anything worth mentioning, I finally decided to return to college. Fortunately I’m doing a lot better this time around and I expect to graduate this Spring with a BS in civil engineering.
College women didn’t find me any more attractive than high school girls did. 
As far as academics go, not much difference. I didn’t find most classes difficult, but I didn’t find most particularly difficult either.
Congratulations, Tabco! It’s never too late.
For me, a huge part of my identity in high school and previous years was blowing the academic competition out of the water. I only had one real competitor in high school. She ended up Valedictorian and I was Salutatorian. Then I went to an elite university… And got my ass handed to me. I was surrounded by students just like me, and many who were by far my intellectual and academic superiors. And they knew stuff I had never learned at my mediocre high school. I just wasn’t special anymore. It was a huge adjustment.
And I wasn’t some sheltered trust fund baby either. I left home at 17 and I’d been supporting myself and trying to get my crap life together. Academics were all I had to give my life meaning at the time. I had to withdraw for a year, but I persevered in the end. And I got a wicked smart husband out of the deal, so no regrets.
This, exactly. Even in the last year of high school, you could get into trouble for being late or skipping class. You had to bring a note from your parents for an excusable absence, and your parents had to sign your report card to indicate that they saw it. Your parents might be called if you were absent too often, or if your grades mysteriously slipped.
All that changed when I started university. Suddenly, nobody cared if I was skipped class or was late. Hell, no longer did school start at 9:00 AM every day, like high school did–I might not have a university class until the afternoon. I didn’t have to show my parents my grades. It was wonderful!
Until the downside became apparent. If you skipped class, or were habitually late, you might miss something important that would be on the exam, and wasn’t going to be repeated in subsequent classes. Sure, you could attend class hung over, but how much would you understand and retain? Your professors and instructors didn’t care; they never sent anybody to the office, as happened in high school.
My point is that with nobody overseeing your education, as you had in high school, you had to take responsibility for it yourself. If you succeeded, great! But if you screwed up and went off the rails, well, it was your problem–nobody else’s. You couldn’t blame anybody; it was your own fault. You were finally in charge of your own education, and it was up to you to take advantage of what was offered to you. This is what hit me the hardest; and thankfully, I learned it early in my university experience.
Standing in the parking lot of Texas Stadium, I realized I could never be a high school student again. I could be a college student multiple times in the future, but High School was OVER.
(the acoustics were terrible- 99% of the stadium was empty and voices echoed endlessly)
I had a somewhat opposite experience as far as workload. In high school, I did an International Baccalaureate program, which was just oceans and oceans of work. Even though I went to an elite engineering school, the workload my freshman year of college was lower than my senior year in high school. The work was harder in some senses (college math was taught at about 8x the rate that we learned in high school), but the total amount of time spent on homework was about equal. And instead of 8 hours of class + 4 hours of homework + household chores, I had maybe 4 hours of class (some of which I quickly discovered I didn’t actually have to attend), a 3 minute commute, maid service and a dining hall. I had hours of extra free time every day and way fewer actual responsibilities. It was awesome!
This was my experience as well. I went to an incredibly difficult prep school. When I got to college, it was easier than high school. I expected a continuation of challenging classes, but it didn’t happen. As a result, I ended up cruising and not working as hard as I should have.
Another thing I noticed was that expectations for women were lower and often condescending and demoralizing. For example, I had taken 2 years of calculus before reaching university. I was discouraged from taking one Physics track because it used calculus and would be too hard. At that time, I lacked enough self-confidence to push back. To a certain extent, I regard university as wasted time.
What hit me hardest about going to grad school was discovering that I really didn’t have any interest in research and that I had no plan in life beyond “get a PhD” (which suddenly seemed like a terrible idea).
College is a great place to discover how dumb you are.
I’d aced every problem set, quiz, and exam in high school physics. I advance placed out of first term calculus (which ended up being a lot more work than I thought it would be). My thought was to do the same for Physics, but it wasn’t an option. So I signed up for the math-based first tern physics course (colloquially known as “Physics for Masochists”), figuring it would be easy.
I ended up in the weekly “help” classes. It turned out to be a lot more difficult than I thought it would be.
But I learned, and passed the course pretty well, eventually (It was Pass/Fail, so I don’t know exactly how well.)
But it was a real wake-up call.