The OED that's being referred to here is a 20+ volume set that costs about a thousand dollars: https://global.oup.com/academic/product/the-oxford-english-d.... University libraries will probably have a copy or two, and I suppose some high school (9th-12th grade) libraries might have a single rarely consulted set, but I'm doubtful any elementary schools in the US have one.
The best evidence I can give for its exclusiveness might be the link on the front page of the official OED site http://www.oed.com to the information about the print edition: http://public.oed.com/about/the-oed-in-print-and-on-cd-rom/. It goes to a page not found. Rather than being a standard companion book, apparently so few copies of this are sold that no one has bothered to fix the broken link!
http://www.oed.com/staticfiles/oedtoday2/oxford_and_the_dict...