Season of Ponies

From Author Wars - https://authorwars.com/publications/season-of-ponies-548551.html

Overview:

Title: Season of Ponies
Author: Zilpha Keatley Snyder
Year: 1964
ISBN-10:
Publisher: Atheneum
Price: $3.25
Pages: 133
Binding: Hardcover
Type: Novel
Title Reference: Season of Ponies
Notes:
"First Printing January 1964" on copyright page of Archive.org copy (Third Printing, August 1965).

Price from listing in "Atheneum Books for Children Spring 1964", School Library Journal 10.7 (Mar 1964) p12; this one ages "8-12; $3.25".

Contemporary review by Kirkus, as posted online 2012 (see the novel record), reports release date March 20, 1964.