Nottingham uni has it's own testing regime in place - it hands out spit test kits to all the students on a rotation, and then if that proves positive the students go on to take a NHS test. This has picked up a huge number of asymptomatic positive cases ( I last heard that about 80% of the positive cases were asymptomatic) This mean that, without the uni doing testing, all those cases wouldn't be picked up, and those students would be spreading the virus around. I suspect that, if other unis did their own testing in this way, (and some of them do) their positive case rate would be very very high too. On first testing, 25ish students in my DDs halls were positive, and so all those in their household had to isolate. On the second testing, only 3 were positive, so this regime is working to contain the virus to a certain extent