Based on historical categorization, Iranian languages are divided into three main periods including: ancient, middle and new. In the old secondary school literature textbook, History of Literature (1), and in the modern secondary school literature textbook the Literary Science and Techniques (1), a lesson is dedicated to Pre-Islamic literature, languages and alphabets of ancient and middle Persian era. The purpose of this descriptive article was to compare the quality and quantity of the content of this lesson in the two textbooks. The study indicated that the designated pages to pre-Islamic Persian literature were cut into half in the new educational system in 2019 in comparison to the old book of 2013. In the old book, three items were noted to be corrected, and in the new book, three sentences with incomplete or mistaken information were found. Analysis of the table on page 39 of Literary Science and Techniques (1) showed that out of 36 comparisons of alphabet signs, 30 items needed to be corrected, completed or deleted. The reasons and suggestions to correct the mistakes were provided. It was also emphasized that ancient Persian language was just one of the languages of the ancient period, hence, it must not be used as an equivalent for that period. Investigation of the written literary works of pre-islamic period showed that that poetry existed in the ancient and Old Persian language. In the Avestan language, the weight of a group of syllables and some others was multiplicative. In the Middle period, the group of Western languages, the weight of syllabic or percussive poems was recognized to be multiplicative.