(Portland, OR)  --  Christmas vacation will be extended by at least a day for students in Portland-area school districts.  Snow and ice over the weekend have prompted officials to cancel school today for Portland Public Schools, as well as for Reynolds, Gresham-Barlow, David Douglas, Battle Ground, Camas, and Washougal.  There will be a two-hour delay today in the start of school in Beaverton, Lake Oswego, Canby, and Vancouver.