This research considers the use of one of the strategies of the concept-based learning, which allows students to absorb knowledge in a universal way, on the subject of mathematics when teaching secondary school students with this method and its features.

According to the traditional two-dimensional model of the curriculum, the content of knowledge is presented within certain topics that contain data. The given data usually form the student's ability to know and understand. It is observed that students in this type of model usually study factual information mostly and are not able to answer questions of the high order thinking types for analysis and evaluation (Medwell, J. & Wray, D., 2020). The acquired knowledge remains in the state of individually isolated data without logical relation between facts and conclusions. This does not contribute to the revitalization and development of deep-level mental activity of an individual.

Meanwhile, conceptual learning assumes not a simple comprehension of knowledge through teacher delivering but full immersion and skills focused curriculum (Erickson L., 2017). According to Wiggins and McTighe (1998), "A concept is a principle or conception of a broad-minded, long-term character that transcends the context of origin, time period, and material content." Based on the given definitions, the acquired knowledge should not be limited to a certain level, the knowledge should be used in a variable manner, on a wide scale.

Unlike a two-dimensional curriculum based on facts and skills, concept-based learning is based on big ideas (Murphy, 2017), not just subject content. And the ideas that arise from knowledge are wide-ranging, interconnected and interdisciplinary. For example, through concept-based learning, students can explore the big idea of ​​"change," from patterns in mathematics to civilizations in social studies to life cycles in science. They become critical thinkers, develop the ability to solve problems creatively.

According to the results of the monitoring of knowledge, conducted at the beginning of the academic year, it was found that students struggle in performing tasks that require higher order thinking skills. The rate of completion of tasks assigned to mathematical modeling, which requires analytical skills, was 47%, while the level of completion of tasks requiring data collection and processing was 68%. The results of monitoring showed that although students have a tendency to perform calculations based on theoretical knowledge but analysis, evaluation and drawing conclusions are difficult for them.

This made the relevance of this research to study and draw conclusions on how the use of comparison and contrast strategy contributes to the ability of middle school students to connect individual facts and the formation of inference skills.

In this context, teaching through concept-based approach a teacher needs effective strategies to develop thinking skills of students. One of such strategies is a compare and contrast method that is aimed at drawing conclusions on the case studies by distinguishing similar situations and contrasting phenomena between two or more concepts.

The purpose of the study is to determine the impact of the comparison and contrast strategy of teaching on the basis of concepts on the formation of high-order skills of middle school students.

We also aimed to identify the difficulties that arise when using this strategy for students of this age to further find the best solutions on them.

Research questions:

-          To what extent does the compare and contrast strategy affect the development of students’ high-order thinking skills on Maths lessons?

-          What are the possible difficulties students may face when learning through the strategy and method?

This research is qualitative as the main method was to study five focused groups of students of grade seven (84 students in total).

Document analysis including evaluation of students’ works and results, lesson observations, survey and interview methods were used in data collection. A comparison was made based on the results of the two sections, which are high in importance, and the changes in the students' knowledge and skills were differentiated. Before the study, the program of the 7th grade was analyzed and micro-concepts related to the subject were determined. The main concepts that are convenient for using the strategy have been selected. Model lesson plans were developed according to the "compare and contrast" strategy of concept-based teaching. The pattern of planned lessons corresponds to the learning objectives in the curriculum. Lesson plans included questions and tasks aimed at revealing the vital importance of basic concepts such as numbers, equation, dependences and patterns, functions. The tasks aimed at the student's analysis and collection of information. In addition, instructions were attached to guide the student to independently research and plan actions to complete complex assignments accordingly. These activities were organized in the form of individual work, pair work and work in small groups. In order to determine the effectiveness of the method being used, a questionnaire was taken from the students. The personal interview, which included structured questions, helped to find out the opinion of the students, determine the priority directions, and make plans in a new direction accordingly. According to the results of the survey after the lessons with the compare and contrast strategy, 70% of the students indicated that it was interesting to solve the tasks given to identify patterns, establish connections, and make conclusions by experimenting. They mentioned the need of using logic in these tasks and found them interesting. However, 32% of students reported that they have difficulty understanding the terms of tasks of practical importance. 18 out of 30 students who participated in the personal interview preferred to solve problems in class using only ready-made formulas and properties, but 12 students preferred to conduct research and draw conclusions on their own. 60% of the students emphasized that they liked to create definitions for new concepts and create rules on their own by describing and observing their features. According to them, it helped to remember the necessary definitions better. Two out of 14 students who liked to solve practical problems answered that it would be practical skill in the future.

The research made it possible to differentiate the effectiveness of the methods used in teaching based on the findings. To conclude, one of the most effective ways is to identify two or more related ideas and conclusions, and to give students tasks that combine these concepts or offer small research works. In this case, the educational goals of several subjects are covered by one task, and mutual communication is realized in a real way. The student uses the knowledge and data acquired to perform the task, determines and analyzes their connection, and accumulates on the basis of deceptions and reaches the level of assessment of thinking skills. Although integrated learning, which is usually used to transform knowledge, realizes interdisciplinary communication, in many cases it can lead to the creation of artificial communication. Therefore, in addition to small research works offered in class, giving creative tasks such as experimenting and designing outside of class or as homework allows students to think freely. Thus, based on the findings, it is clear that the implementation of the strategy alone without the stage of learning facts and theories is not possible. Using the compare-and-contrast strategy, students conducted analysis while completing small research tasks. Pupils distinguished common properties or features of the given concepts, classified them, and determined the interconnection. Based on the results of their analysis, they made a general conclusion. In this way, it was assumed that they would learn to perceive the main concepts in mathematics as a big idea related to the world, instead of taking them at the level of the topic as usual.

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