One of the skills necessary in dealing with the digital era in the 21st century is communication skills [1]. The important part of communication skill in the field of science is argumentation skill [2].

Argumentation skill is an important requirement that must be mastered in science because science learning not only sees how natural law works but also to be able to explain how natural phenomena occur and how it goes in the future. Osborne, Erduran, and Simon emphasized that argumentation is crucial in constructing scientific knowledge, as it allows for discussion of facts, prevailing theories. Thus, argumentation skills should be integrated into science learning. [3]. Socio-cultural view emphasizes on the social interaction in the process of learning, thinking, the ability of thinking critically honed through discussion, argument, experience exchange among students [4, 5]. Teaching argumentation skills in structured science learning is essential, as argumentation in science has unique characteristics. This skill helps improve scientific knowledge by allowing students to construct answers aligned with scientific concepts [6]. Considering the explanation above, argumentation skill is important to develop in the learning process.

Comparative analysis of the results of summative assessment for a unit and for a term showed that among the parallel of 8^th  grades students, one of the 8th grades regularly showed low results.  In the first term, the quality of knowledge was 59.8%, in the second term - 63.5%. This is a low result in comparison with the results of other 8^th  grades. Analysis of students' oral and written answers revealed the following problems:

-      inability to search, select and interpret data from different sources. This is especially important for arguments that are based on facts.

-      inability  to analyse information, highlight the main points and link scientific facts.

-      Inability to formulate a well-organised, scientifically and valid response.

At the ages of 13–14, according to Piaget's stage of formal operations, students develop abstract logical thinking, learn to reason hypothetically, analyze complex concepts, identify cause-and-effect relationships.

We assumed that the use of a PBL (Problem based learning) model would support the development of argumentation skills in 8th grade students, given the increase in the number of questions requiring argumentation as they proceed to the upper grades.

PBL stimulates students' activity, encouraging them to use not only the knowledge gained from the teacher, but also other resources to search for information. This method promotes the development of reasoning, analyzing and theoretical thinking skills.  In the PBL model, students acquire problem solving, critical thinking, group work, and reasoning skills through collaborative discussions and the use of online resources [7].

The correlation analysis by S.N. Pratiwi, others shows a strong positive relationship between argumentation skills and students' knowledge quality, highlighting the link between argumentation skill development through problem-based learning,academic performance [8]. PBL helps students develop flexible knowledge, problem-solving skills, independent learning, cooperation, and intrinsic motivation [9]. It enhances conceptual understanding and can be successfully implemented when teachers integrate argumentation skills into the PBL model [10].

Research Question:

How does the use of PBL affect the development of students' scientific argumentation skills?

Sub-questions: 

1. What aspects of critical thinking are most actively developed in the context of argumentation when using PBL?
2. How does the use of PBL improve students' ability to make logical, scientific arguments when solving a problem?
3. How do we evaluate students' argumentation skills when using PBL?

The PBL model enhances critical thinking and argumentation skills in 8th grade students, boosting motivation and knowledge quality. It teaches students to construct logical, scientifically-based arguments in research and interdisciplinary tasks. Assessing these skills requires a comprehensive approach, including written work, oral presentations, group interactions.

16 students from the 8th grade (Kazakh-medium class) who showed low results in summative and formative assessment works were chosen as a focus group for action research. Questionnaires were collected before and after action research. The aim of the questionnaire was to assess the level of learning motivation, students' interest in acquiring new knowledge and the degree of their involvement in the educational process. Taking into account the age features of 8th grade pupils and their difficulties in formulating structured answers to high-level questions, the SExI (Statement, Explanation, eXample, Interpretation) method was applied, which is based on the Toulmin model [11]. This method allows students to formulate an algorithm for scientific argumentation and improve their ability to provide high-quality, evidence-based answers to questions that require higher-order thinking skills. The use of the SExI method facilitated students' ability to complete tasks by structuring their thoughts in four sentences. This enables the teacher to easily determine the level of argumentation skills. Two types of data were used within AR: Pre-test to assess initial knowledge level, Post-test to determine changes after learning to analyse the effectiveness of PBL method. Pre-test, Post-test allow to measure the progress of students. The pre-tests help teachers to adjust the curriculum at the beginning, while the post-tests assess where changes need to be made to improve comprehension and recall. Comparing the results of these tests provides an opportunity to further analyse specific areas for improvement [12]. While not all students will show excellence by the end of the course, pre-tests also show students their personal growth. And it builds their confidence and motivation to succeed. To analyse the relationship between the use of PBL and the development of argumentation skills, the Spearman correlation coefficient was determined using IBM SPSS program. Correlation coefficients are used to measure the strength of the linear relationship between two variables. A correlation coefficient greater than zero indicates a positive relationship, while a value less than zero signifies a negative relationship [13]. Nonparametric statistical tests using Spearman's Rho correlation were then used to analyze the data. The effect of Problem Based Learning on argumentation skills in addition to influencing physics learning, also has a positive effect on increasing the average students' mathematical argumentation skills [8, 14]. The SExI technique was applied throughout the 3rd and 4th terms. Before completing tasks the teachers reminded of employing the SExI method.

The following findings have been outlined: 1. Pre and post questionnaire results showed that students' motivation increased from 3 to 5 points, and teamwork techniques boosted engagement by 24%. 2. Pretest results using the SExI method revealed that 23% of students had high argumentation skills, 57.6% had medium and 19.4% had low ones. 3. Post-test results: analysis of students' oral and written responses using the SExI method for the focus class revealed that the proportion of students with high argumentation skills was 44.5%, a 21,5% increase from the beginning of the study. The average level was demonstrated by 55.5% of students, and the low level was completely absent, which indicates the positive impact of PBL on the development of argumentation skills. 4. In the third term, the quality of knowledge in the experimental group was 78.9%, while in the control group it was 83.9%. In the fourth term, using the PBL method, the results in the experimental group reached 88% while the control group reached 90%. This indicates that the lower performing students were able to reach a level of knowledge comparable to the students in the strong group. 5. To analyse the relationship between the use of PBL and the development of argumentation skills, the Spearman correlation coefficient was determined using IBM SPSS program. The results of the correlation test (two-sided significance < 0.01) showed a positive relationship. The Spearman coefficient was 0.622 > 0.05, indicating a high correlation between PBL and improvement of argumentation skills. 6. The study found that developing critical thinking skills, such as analysis, evaluation, and problem-solving, significantly boosted students' cognitive engagement. This is evidenced by a 28.2% increase in knowledge quality by the end of the academic year. The participants showed improvement in evaluating information, forming conclusions, and finding effective solutions.

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