File Pl-modified_data.cvs contains raw data obtained in the experiment described in the paper “The ‘PL-modified’ computer game system as a diagnostic tool for measurement of higher mental actions by middle-school students”. Descriptions of the variables are provided in the “data_frame.cvs”. In the present study the computer game system named ‘PL-modified’ was tested as a diagnostic tool for measurement of higher mental actions of analysis, planning, and reflection by middle-school students. The ‘PL-modified’ is a computer system where participants have to line up the balls of one color to get points. The task lies also in its rules (or patterns) of how the balls will be presented at every follow-up game turn. Participants have to understand these rules and use them further by proceeding with successful game performance. Thus, the abilities to analyze the rules (mental action of analysis), to manage with the game patterns to get more points (mental action of planning), and to understand how to act when the rules changed (mental action of reflection) are aimed to be in the focus of the present study and be measured by the elaborated computer system. Two groups of participants from two different schools – with a traditional educational system (school 2) and that one where educational process is aimed to be adhered to the ‘theory of developing education’ teaching methods (school 1) participated in this study. Abstract intelligence was also assessed. We suppose that the students from the school 1 will exhibit the higher level of the game performance than those students from the school 2 because of the highest level of mental actions, but not intelligence. The whole testing procedure was lasting for two lessons (45 minutes for each lesson). At first lesson participants were introduced to a game content and then were playing the game by sitting separately for a computer. At second lesson abstract intelligence was measured. It was revealed that participants from the school 1 surpassed those from the school 2 in their level of the mental action of planning and intelligence. Moreover, the parameters represented three researched mental actions of analysis, planning, and reflection exhibited robust interactions separately from the impact of intelligence by the group of participants from the school 1. And it was statistically confirmed that the three variables were correctly represented and scored by the elaborated game procedure. The results let clearly characterize the discriminant properties of the elaborated computer game system which is supposed to measure certain mental actions. The revealed data make to outline the appropriate prospects for the usage of the ‘PL-modified’ system as a potential diagnostic tool in education so far the system obtains psychological and technical advantages during the testing process. If you have any questions or commentaries, please feel free to contact us at firstname.lastname@example.org (Evgeniya Gavrilova).