@TeacupDrama
1,400,000 out of a population of 65250000= 2.1%
70 out of 2573 positive tests = 2.7%
If everyone had the same chance of getting the virus, we would imagine that 2.1% of the positive tests would come from people in schools. That would be 54 positive tests. At 70, we have slightly more than that in reality, not less.
If my hypothesis was that school children had the same chance of catching the virus as anyone else, I certainly wouldn't reject that hypothesis on this evidence. If I did reject it, it would be to say that they were more likely to catch it, rather than less, but to be honest, I think it's probably within a reasonable confidence interval.
If my hypothesis was that school children are less likely to catch the virus than adults, I'd be questioning that right now.
Of course, being able to catch the virus doesn't mean being able to transmit it, but I always think there's an element of straw clutching in that argument. Fortunately, however many children become positive, the chances of them dying are vanishingly small, thank goodness. I don't think schools are a risk to children themselves. However, although 70 is a low number in absolute terms, I don't think it bodes particularly well for the assumption that children will be any less infectious than adults.