I think if you set it out from the begining, that you dont do school care, then paretns know when the time comes that they'll have to find alternative care for the one in school. Some will be ok w having their kids at different daycares, others will not. So depending on the situation, you may very well have 2 spots to fill come Sept (the school age child and the younger sibling) but if you and parents agree upfront what is going to happen then you can plan for it....