The current advice from the Government is that no school should close in response to a suspected (or confirmed) COVID-19 case unless advised to do so by Public Health England. I do not think this is correct advise, if "confirmed" schools should be closed for deep clean with pupils sent home.
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If we keep sending pupils into a "confirmed" area - this will help spread the disease. If one student has been confirm it is very likely others would have it too.
Keep them all away from each other should be the next phase once discovered in a location.