I've just finished working in a childcare centre and we sent kids home for (apart form the obvious chicken pox etc..) 2 runny nappys in a day, green snot (again not clear, and depending on the amount too.....a little is ok but if it's a constant stream they get sent home), and temps. They are the common ones. I don't know about legal requirements and about how much truth is in the green snot thing but I've always been told by the GP that green snot means an infection of some sort.