@fourminutestosavetheworld We have to provide a face-to-face or equivalent online experience for all students. The online equivalent must be available for all students who have a valid reason for wanting it, including students who have tested positive but consider themselves well enough to work.
When we taught during the pandemic, valid reasons included illness, isolating due to contact, students who were unable to travel, UK or international students who wanted to return home, students who were medically vulnerable and students who just generally felt unsafe. At the moment, we have cut the list to just students who are not actually allowed to attend, such as those who have a positive test and those who cannot travel, but in the event of another widespread outbreak, this may change.
We have been told we must provide an online equivalent for every face-to-face activity we do. This online equivalent must be of approximately the same duration and provide the same experience and learning outcomes as its face-to-face equivalent.
If a student is too ill (or otherwise indisposed) to attend either in person or online, then it is up to them to make up the work but we are expected to support them in doing this. If this applies to a significant number of students for a significant part of a module, as in the half the class example, we would be expected to put on repeat sessions either in person (which is impractical given space constraints) or online for anything like seminars and practicals where there is no recording and engagement is important.
@LoonvanBoon To answer your question on social spaces, at the university where I work, there will be no social distancing required in social spaces such as the students union, cafes, bars, sports facilities, etc. There will be social distancing required in the library study spaces, teaching rooms, offices and, where possible, corridors, atriums and other indoor spaces within academic and administrative departments. As far as I am aware, the university is making a distinction between places students have to go, i.e. teaching and study spaces, and places they can choose to go, i.e. social spaces, so that students can decide for themselves the level of personal risk they want to take.
Unless we have significant welfare concerns about a student, we will be allowing all students to attend one-to-one meetings such as personal tutoring, office hours and similar on-line if they want to. It was something they really liked and there was a massive increase in attendance.