Allow me to paint you a picture: Imagine walking the halls of a somewhat small, yet friendly high school of around 1,000 students and around 200 senior students. You ate lunch with the same people every day and shared classes with them as well. The same people got in trouble almost daily for doing the dumbest things you could ever imagine. High school for me was homey, and sitting in class, especially as a senior, the teachers constantly drilled in our heads everything that wouldn't be tolerated once we got to college, but if only they knew the reality of the situation.
The fun of the situation kicked off after moving into my college dorm. There's nothing more intimidating than going from a smaller town and high school to a large school with over 20,000 students. Admittedly it's not hard to feel lost people-wise in a place like that, so that made the situation a major transition. I had been so used to seeing the same people every day, but in this new environment, I now find myself with a steady group of people but also going on a scavenger hunt in hopes of finding them even just to say "hello". It's really like everyone poofs in thin air sometimes, keeping me on my toes, to say the least.
I vividly remember my high school teachers always mentioning how the professors in college wouldn't hold our hands through the class or spoon-feed us information, which might be one of the only things they mentioned that's actually true. Some classes may be only 50 minutes while others are 3 hours and let me tell you, they value filling up every minute of the class even down to the seconds at times, and if you're lucky, they might actually let you leave early. For the most part though, with this in mind, the classes are down and dirty with an abundance of information that you'll only get every word of in your notes if you're lucky. Don't get me wrong, if you're confused, the professors are happy to help but you have to get it yourself. What you take from a class is your own doing so it's important to remember to always be as engaged as possible and have those short after-class conversations with your professors to get yourself on the right track.
A majority of my high school teachers were actual saints (and not because we were a catholic high school). You would never hear a single swear come out of their mouth or a joke deemed inappropriate. This is the complete opposite in college. Freedom of speech especially rings true as nearly every professor drops an f-bomb here and there or usually unintentionally leave an adult joke on the table open for interpretation. I especially loved one English class where my professor was talking about the Great Chain of Being and mentioned how the lion is at the top of the animal chain and was compared to a donkey (aka an ass), therefore he eats the donkey/ass. Welcome to the adult world, there are no pure minds here.
My high school teachers used to hound us about our attendance and behavior like nothing else. If you were noticeably late for class or wouldn't listen at all, you would get "personal" detention after school with that teacher. However, there is no such thing as detention in college which is such a huge change after having four years of a majority of your classmates getting one almost every day. In college, you get a certain amount of days of unexcused absences per class and the professors honestly don't care much (or at least don't seem to) because your success in the course is your decision. I'm also a fan of reading a syllabus that mentions marking someone absent for sleeping in class because if you really think about it, they're not present and therefore aren't there. The only "behavioral" things that seem to matter in college are being safe and respectful and whether or not you're cheating/plagiarizing, but mostly, the professors might just goof around with you if they're that type of person.
So yes, high school and college do have their significant differences and, for the most part, life in college isn't exactly as described by high school teachers. The overall vibe of college feels a bit more chilled out than in college and you're left to your own devices much more while still being able to find the resources you might need. You'll get a lot of generalizations instead of step-by-step instructions like you did in high school project wise, teachers won't be coming to you if you don't find a partner for group work, and your assignments won't be announced 20,000 times a week (your syllabus is your lifeline). In a way, college is brutal but also great with so much freedom, but you shouldn't take it for granted. You are more responsible for yourself than ever before.