I am a lecturer (US equivalent: assistant professor) at a research intensive UK university but also very familiar with the US system where I did my undergraduate studies and some graduate work. I thought it might be useful to give a more detailed look inside the UK system, at least from one department.
Here, exam marking (grading) is done by academic staff rather than postgrads (as xnn already said elsewhere) - and in our department it must be done by the person in charge of the class rather than someone unrelated (we have a lot of team teaching, and I don't think there are any academics here, even full professors with major grants, who are excused from contributing to teaching). This person is also responsible for designing the exam which goes through a quality control process - must be checked off by another member of academic staff, and then approved by an exam board which goes through question by question to assess how each question relates to the intended learning outcomes of the class, then going to an external exam board who also approve the exam.
We also have independent second marking which is a serious time sink and major bone of contention - marking is not just done by the course convenor, but a second academic independently marks each exam essay and then come to a consensus about the final "agreed" mark. Additionally, one other internal person surveys those marks, particularly for marks just under a grade border, and discusses grading scheme with the first marker if there are problems. And then, as mentioned the external examiner goes over the exam paper, marking criteria, and a sample of the essays at different levels. And if that were not enough we then have a big meeting with all the parties involved to discuss exam marking issues across the whole degree program.
As you may expect this is an astounding amount of work - the need to assure high quality marking through such heavy efforts is closely related to the typical tendency in many UK institutions to offer no feedback to the students about the details of why they were given a certain mark. Coming from the US this feels very extreme: our students in the UK write essays without notes in in-class examinations and then never see them again, nor indication of why they earned the mark they did. So I very much hesitate to say this is better than the US system where students have access to their exams and thus some amount of accountability is forced by student feedback.
Thanks for those details!
This is incredibly different from the way it's done at the US and Israel (I've taught at Harvard and Hebrew U), where exams are graded by grad-students TA, and certainly no more than one grader each exam.
This leads to a temptation to grading by one's own own highly informal curve, as well as to extreme grade inflation in top US universities.
The UK way is far better, except for the lack of feedback.
One of many problems with the contemporary university system is that the same institutions that educate students also give them their degrees and grades. This obviously creates massive incentives for grade inflation and lowering of standards. Giving a thorough education requires hard work not only from students but also from the professors. In the absence of an independent body that tests that the students actually have learnt what they are supposed to have learnt, many professors spend as little time as possible at teaching, giving the students light workloads (something most of them of course happily accept). The faculty/student non-aggression pact is an apt term for this.
To see how absurd this system is, imagine that we would have the same system for drivers' licenses: that the driving schools that train prospective drivers also tested them and issued their drivers' licenses. In such a system, people would most probably chose the most lenient schools, leading to a lowering of standards. For fear of such a lowering of standards, prospective drivers are in many countries (I would guess universally but do not know that for sure) tested by government bodies.
Presumably, the main reason for this is that governments really care about the lowering of drivers' standards. Ensuring that all drivers are appropriately educated (i.e. is seen as very important. By contrast, the governments don't care that much about the lowering of academic standards. If they would, they would long ago have replaced a present grading/certification system with one where students are tested by independent bodies, rather than by the universities themselves.
This is all the more absurd given how much politicians in most countries talk about the importance of education. More often than not they talk about education, especially higher education, as a panacea to cure for all ills. However, if we look at the politicians' actions, rather than at their words, it doesn't seem like they actually do think it's quite as important as they say to ensure that the population is well-educated.
Changing the system for certifying students is important not the least in order to facilitate inventions in higher education. The present system discriminates in favour of traditional campus courses, which are both expensive and fail to teach the students as much as they should. I'm not saying that online courses, and other non-standard courses, are necessarily better or more cost-effective, but they should get the chance to prove that they are.
The system is of course hard to change, since there are lots of vested interests that don't want it to change. This is nicely illustrated by the reactions to a small baby-step towards the system that I'm envisioning that OECD is presently trying to take. Financial Times (which has a paywall, unfortunately) reports that OECD are attempting to introduce Pisa-style tests to compare students from higher education institutions around the world. Third year students would be tested on critical thinking, analytical reasoning, problem solving and written communcation. There would also be discipline-specific trials for economics and engineering.
These attempts have, however, not progressed because of resistance from some universities and member countries. OECD says that the resistance often comes from "the most prestigious institutions, because they have very little to win...and a lot to lose". In contrast, "the greatest supporters are the ones that add the greatest value...many of the second-tier institutes are actually a lot better and they're very keen to get on a level playing field."
I figure that if OECD get enough universities on board, they could start implementing the system without the obstructing top universities. They could also allow students from those universities to take the tests independently. If employers started taking these tests seriously, students would have every reason to take them even if their universities haven't joined. Slowly, these presumably more objective tests, or others like them, would become more important at the cost of the universities' inflated grades. People often try to change institutions or systems directly, but sometimes it is more efficient to build alternative systems, show that their useful to the relevant actors, and start out-competing the dominant system (as discussed in these comments).