Individual sellers and third party companies such as eBay.com and Amazon.com, respectively, offer teacher editions and answer key booklets for a variety of subjects. Textbook publishers such as Houghton Mifflin Harcourt also sell teacher editions at full price.
Answer keys typically come within the teacher edition of the textbook used in class. New and used copies can be found through individual sellers or warehouse companies such as Amazon.com.
With schools becoming more technologically minded, many test and assignment answer keys are found online through the textbook publisher's online book access. To get to these answers, a certified teacher login and password is required.