I am not certain that the demographics of infected people in a country that has not seen widespread community transmission necessarily carry to one which has.
From the report, you can see that they tested two groups. One group was high risk, and most of these had travelled abroad. That there may well limit the number of school aged children in that sample.
The other group was randomly selected. Of this second group, only 100 in total were infected.
100 people, from a different country, in a totally different stage of an outbreak, is not a good quantity of data to draw conclusions from for us in the UK.
In the early stages of the South Korean outbreak, infections were largely amongst a single church group. In Germany, the initial outbreak also had a very different age profile to other coutries.
I would be extremely cautious about drawing general conclusions from such a small study.
What we need to ask ourselves is:
Where is the equivalent data from the UK?