The first two years were a lot like high school, except the people were slightly more tolerable in some ways. High school for me involved a lot of frustration with my classmates' anti-intellectual attitudes. For instance, a real conversation from high school:
Me: "Hey guys, I've been noticing recently that even though it certainly feels like we have some amount of choice and self-determination, since we can only make one "choice" from a set of options, I don't think it's possible we can ever know whether the universe is deterministic or allows for choice. Do you guys have any thoughts on this or can you think of any ways we can know this sort of thing that I've missed?"
Friends: "Dude, shut up. It's lunch period. This is no-thinking time."
In med school, people will usually be happy to talk about this sort of stuff (although their points are more frequently half-baked/concrete/uninteresting than when talking with fellow philosophy people in college, which I miss).
The social dynamics were similar in that you spend a lot of time with the same people and in my program (which was PBL), everybody got out of group at the same time and had lunch together. People were cliquey, with groups revolving around, typically, either personality or specialty. The "California people," for whatever reason tended to hang out together. There were a few people who were more philosophically trained/inclined, who I hung out with (however, most of these people for whatever reason were also planning on doing psych, so it's unclear which initially formed the basis of the clique). However, I felt the cliques were a little less exclusive and people were more friendly to out-groups.
In the clinical years, I find it hard to compare to high school. It's much more comparable to when I had a ****ty summer job in college than high school. In my ****ty summer job, there was one vagrant 19 year old who would show up to work high and ask me to drive him home because he lost his license due to a DUI. On clinical rotations, there's often some idiot who refuses to preround on patients, never prints out notes, never gathers wound supplies, can't follow up on a fax, etc. and generates more work. At my ****ty summer job, I would often get dismissed right before I would hit overtime hours. In the hospital, I often get dismissed right before signout. In both situations, it was framed as "you get to go home early." In both situations people asked me incredibly dumb questions or expected me to know **** that I had no business knowing: "Excuse me, med student who is not part of my medical team, my doctor said I might want to have some procedure, I don't remember what it was but I think it starts with an H. Anyway, my insurance is X and I wasn't sure whether that thing will be covered. Do you know about this?" Both the hospital and my ****ty summer job involved unscheduled lunch breaks at the attached food court which mostly sells ****ty food. Both the hospital and my ****ty summer job involved some cursory day of "training" after which I knew some esoteric random stuff about my work environment but still didn't know things like what to do on my first day.