Fed up with my coworkers

So I just finished my second year at uni, and over the summer I’m working full time in my uni’s international department, overseeing the programmes that we run for students abroad who visit the city and practice their English. It’s a fairly standard admin job - booking trip and coach tickets, filing dietary requirements and sourcing catering numbers, managing the information sent out to our residential advisors, creating materials for students, etc. It’s by no means a super difficult job BUT it’s important we get things right as otherwise it can very quickly go off the rails.
For context, I held this same job last summer (under a different manager), as well as over the most recent break at Easter (under my current manager), so I do know the ropes - I had a similar office job before this, too. Basically all of my colleagues are new to the role but have all just finished their fourth year and are graduating, so they’re slightly older. As a result their training was basically left in my hands but I have zero manager experience so probably missed some gaps.
What frustrates me is that none of these coworkers seem to care about our job. I know it’s only a temporary stop in the grand scheme of life but they are constantly talking about how little work we do and how easy the job is. I can appreciate that I might take it *too* seriously at times but like I said, when you screw up catering info or coach timings all of a sudden your day is ruined and you have 100 students stranded without food/transport/the list goes on. It’s not like there are zero stakes to the work we do.
I do feel I do more work than them at times, although often this is out of necessity as many people around the uni treat me as the “leader” of the program (for lack of a better word). My manager constantly calls me her right hand woman and I’m always the first person to receive info or be asked for a decision despite being on the same wage as everyone else. To be honest I enjoy being in the thick of it and knowing exactly how all our procedures work so I’m not complaining but when things go wrong it feels like a lot of responsibility falls on my shoulders even if I’m not outright blamed for it.
I have two good friends who work more on the academic side of the department, curating the curriculums for students and managing teachers. They are both older than me (35 years older in one case, but that’s another story entirely!) and I do see them as somewhat mentor figures. Both of them insist that I work too hard. They are also two of the only people who I feel understand the importance of some of our work - in a crisis (say, when a student has their wallet stolen), they are quicker to jump in and help me than my actual coworkers are.
I appreciate that this post comes across as a kind of weird rant but I’ve just found myself feeling more and more fed up with the atmosphere in the office recently (I started work mid-June the moment term ended). We just had a busy arrivals weekend with seven new unis so there is always stuff to be getting on with - future materials, liaising with RAs, setting up classroom sites and endlessly more tasks - but no one seems to have any incentive to do these things until they are explicitly told to (either by our manager or by me in anticipation of the former). Yet they always go on and on about how much of a p*** take our job is and how we never do any work.
It sucks because I have a lot of thesis reading I should be getting on with, but every day I come home from work and I’m flat out exhausted because I’ve spent the whole day being stressed and trying to keep my manager happy while keeping up a chill facade around my coworkers who think the whole thing is a joke and can’t understand why I’m so invested.
Any words of wisdom are very genuinely appreciated - thanks for reading this far 🙏