My daughter went to nursery for four years and only once something like this happened. At some point after restrictions lifted, our nursery had 50% of staff test positive for covid. Even in this extremely unusual case, they didn’t close - they called all parents and asked us if we were in a position to make alternative arrangements (grandparents, work from home, take a day off) to allow those who were unable to do so to still bring their kids in and those of us keeping them off got an extra day a month or so later. No-one was forced to change their plans and many were happy to make accommodations to support a nursery that had been so helpful and transparent all through lockdown.