This study aims to develop a valid and reliable achievement test in accordance with the content framework of the 9th-grade Biology Course Curriculum published within the scope of the Turkish Century Maarif Model on the subject of "Organic Matter". The screening method was used for this purpose. The sample of the study consists of 258 9th-grade students studying in two state schools located in the eastern part of Turkey. While creating the test, the following steps were followed: determining the purpose and scope of the test, literature review, writing and arranging the items, performing the preliminary application and analyzing the items, and finally creating the test. Initially, a draft test consisting of 60 questions was prepared. However, as a result of the item analyses, some items were eliminated in order to increase the validity and reliability of the test. At the end of this process, a 40-question achievement test that better reflects the scope of the curriculum and has high content validity was created. As a result, the achievement test, which consists of a total of 40 questions covering the curriculum content framework with an average difficulty of 0.33, an average discrimination index of 0.32 and a KR-20 reliability coefficient of 0.84, has taken its final form.