Are you in the USA? This is a UK-based site although, of course, we welcome questions and answers from anywhere.
The reason I ask is that, by law, a copy of every book published here must be deposited in the British Library but I've just their catalogue and, although there are 272 books with 'Language Arts' in the title, there is no book with that exact title published in, or before, 1959. That suggests that the book you're referring to was never published here.
The US Library of Congress catalogue (or should that be 'catalog', since it's in America?) lists a few titles which might be possibilities but they all seem to have been published within individual states (which means that they'll be hard to track down).
So you might have considerable difficulty in finding the book you require. However, any book of poetry published for schools' use in the 1950s was quite likely to include Walter de la Mare's famous poem 'The Scarecrow'. Perhaps that's what you're actually seeking?
http://allpoetry.com/...-by-Walter_de_la_Mare
Chris