The rules prior to Monday were up to 30 outside weren't they? So if the party was outside they weren't breaking the rules?
I understand the head's frustration, particularly if he wasn't informed of the party even after the outbreak, how could his staff not tell him?
However, it was unprofessional to publicly blame his staff like this. I get that there is so much pressure on headteachers at the moment to keep their school safe, and he didn't want to look bad, but to write it in a letter like that to parents just seems a bit off.
It does beg the question though, should teachers curtail their lives, even within the rules, because of their day job? Teaching is already shitty enough!