This guy seems to be an idiot of highest order.
God forbid if anything like that happens then obviously the school administration will try to keep a lid on that, specially if the school in question is a private school.
What can happen? If precaution is not taken, that poor soul will not only be a carrier infecting other kids but could become more sick and who knows.... succumbing to the viral infection.
Don't get your point or what exactly you wish to convey. It is a random testing program by government - not by school administration or educational department.
With 50 cases out of 25 thousands random tests among about 2 mil students, and one case out of seventeen thousands in the universities - there seem no statistical justification for not opening schools. Data shows that schools administrations are doing well.
There is a risk of infection since the epidemic is not over however, as per data, the risk is not higher to any significant number due to school opening and exceeds the risk in general public.
It is so natural and safe to suggest for keeping schools shut but then there is a cost to this decision. Sooner or later every administration has to weigh the risk and make a decision - and school boards around the globe have generally opted to open school with SOPs And not to forget, that regarding children, their parents are the most concerned party to inspect them, more than governments or school administration.