So how do they get invigilators to work? They travel between schools/colleges/test centres daily, are in contact with hundreds of people a day and then move on to the next school/college/test centre.
Can't have exams if there aren't enough invigilators or they're found to be spreading it to thousands a week.
And what of support staff? You've probably got one or two people who deal with every sick or injured child in school. Who does that once they're in contact and have to isolate/ are ill?
Not just teachers, nurses or doctors on the pointy end of these plans.