This research aims to develop a tool to measure the school readiness of children who will start primary school. Changes have occurred in the primary school starting age following the developments that took part in the Turkish Education System. This change has caused parents to have intense hesitations about enrolling their children in school. As a result of changing the age of starting education, it aims to develop a test that aims to eliminate the question mark in the parents and teachers of children in critical months as the age of starting primary school. This study was conducted with the quantitative research method. The obtained data were subjected to EFA and CFA analyzes by the Amos program. As a result of the research findings, the Attainment Test for Primary School Admission (ATPA-C), which was prepared considering the preschool and primary education aims, took its final form as a 17-item measurement tool gathered together in five factors. As a result of the analyses of the research made with the data of 1285 students, it was detected that the scale had the necessary validity and reliability findings for practice and research.