My policy is pretty similar to mammamia. I think being the mom of 4 kids that you just get used to it in the sense of when one is sick you can't send the other three away or keep them and send the sick kid away. And yes sometimes it went through them all and other times confined to just 1 or 2. I find my daycare is the same way. The children that get plenty of sleep, eat proper foods, play actively tend to fend off more than the others. Large blocks of freeplay allows kids that are feeling sluggish to choose alone and quiet activities. I adjust meal times and what I serve, naptimes, etc. based on the needs of the kids anyways.