I feel like this seems to vary heavily by school and even by intra-school rotational site.
In my (totally unexperienced) opinion, 3rd years should be what sets you up at minimum to do the following:
- Solidify your history and physical taking skills that you learned during M2 and learning more specialized exam maneuvers
- Learn how to do basic medicine work i.e. preround on your patients focusing on what's important, do an H&P for a new admission, present a patient adjusting for audience (full admissions presentation vs soap style presentation), come up with an assessment, and learn how to create a basic plan for further diagnosis and management
- Learn how to work as part of a team (i.e. do what needs to be done, regardless of what benefit you think you may or may not be personally getting out of it)
- Become comfortable interacting with patients
- Learn how to scrub in and at the very least learn how to cut sutures and tie knots
After that, it comes down more into what you're interested in learning, what you're planning on specializing in, what opportunities you got during your rotations, etc. This means that most 4th years will probably know how to draw blood and place EKG leads, but that students will have varying exposure to doing a-sticks, placing IVs, intubating in the OR, placing NG tubes, doing LPs, suturing lacs, doing more stuff in the OR (basically up to whatever the resident/fellow is comfortable letting you do), putting in a-lines, putting in central lines, using ultrasound for any number of things, paracentesis, managing vent settings, I&Ds, etc (those are the things off the top of my head based on things I know students irl have done).
Again, totally depends on what you want to learn, what rotations you're on, and being in the right place at the right time. I've placed a billion NG tubes but I've never done an a-line or placed an IV. I'm sure there are students who've done a couple central lines that have never intubated or done an LP.
I don't think it's a good idea to have new 3rd years (or even new 4th years or really anyone at the beginning of a given rotation) go see new ED consults of unknown acuity, but I think it's something that you should be able to do for people who aren't actively dying closer to the end of 4th year / your rotation.
What the responses here really tell me though is that this is highly variable and depends on when and where you're doing your rotation and how amenable your supervising residents/fellows/attendings are to letting you do things.