And there's more.
'They should get a test, and:
if the test delivers a negative result, they must remain in isolation for the remainder of the 14-day isolation period. This is because they could still develop the coronavirus (COVID-19) within the remaining days.
if the test result is positive, they should inform their setting immediately, and should isolate for at least 10 days from the onset of their symptoms (which could mean the self-isolation ends before or after the original 14-day isolation period). Their household should self-isolate for at least 14 days from when the symptomatic person first had symptoms, following guidance for households with possible or confirmed coronavirus (COVID-19) infection'
Point 10
'If schools have two or more confirmed cases within 14 days, or an overall rise in sickness absence where coronavirus (COVID-19) is suspected, they may have an outbreak and must continue to work with their local health protection team who will be able to advise if additional action is required.
In some cases, health protection teams may recommend that a larger number of other pupils self-isolate at home as a precautionary measure – perhaps the whole site or year group. If schools are implementing controls from this list, addressing the risks they have identified and therefore reducing transmission risks, whole school closure based on cases within the school will not generally be necessary, and should not be considered except on the advice of health protection teams.
In consultation with the local Director of Public Health, where an outbreak in a school is confirmed, a mobile testing unit may be dispatched to test others who may have been in contact with the person who has tested positive. Testing will first focus on the person’s class, followed by their year group, then the whole school if necessary, in line with routine public health outbreak control practice.'