**4. Discussion**

The researchers have discussed the EVs, variance, and correlation between the five types and reviewed the classification results for P-Sample and Q-Sample involved in each type with Z-scores. We have also checked the consensus statements.

In terms of correlation findings regarding each type, since the correlation between all types was low, each type's independence and explanatory power were secured. A strong correlation between Type 2 and Type 4 was observed, which means that the classification intensity of respondents belonging to Type 2 and Type 4 is the highest. In other words, perceptions between the two types of respondents are different prominently. For example, in the case of Type 2, children's participation in the early morning exercise program was recognized by the participants belonging to Type 2 as having a positive effect on revitalizing school life. On the other hand, however, they had negative thoughts about physical and mental reinforcement. In the case of Type 4, they were aware of the advantages of improving their children's exercise skills and increasing interest in PE classes. However, they were not aware of the impact on school life. The discussion based on the results of this study is as follows.

Most of all, respondents from Type 1 showed great awareness of the inclusion of "0-period PE class" into a regular curriculum, not a temporal activity. That is, there is a need for a multifaceted infrastructure in which the "0th-period PE class" can be operated as a regular class. Therefore, expanding facilities, diversifying programs, and placing expert instructors should be considered first to improve the quality of early morning exercise programs. In addition, the respondents were convinced that the "0th-period PE class" helped students develop in various aspects which legitimate promotion expansion of early morning exercise. As a result, this type was titled "urgent legal and institutional settlement of "0th-period PE class": Strengthening facilities, programs, instructors, and publicity".

As mentioned earlier, the early morning exercise program has been activated in Korea since 2010. However, lack of attention from the teachers, low incentives for participating teachers and students, and recognition as an extra-curricular activity are regarded as decisive reasons for the institutional failure to settle down. Lee [21] pointed out several issues each school undergoes in the operation of the early morning exercise program. As a result, the researcher suggested optimizing the program for each school environment, strengthening the role of operating teachers, and improving program facilities. Meanwhile, cooperation between PE teachers, general teachers, and students was emphasized as the most crucial factor for the program's success [19]. For example, Jeon et al. [38] emphasized the theoretical basis for implementing the "0th-period PE class" for middle schools and

applied practical measures to encourage the participation of teachers and students. Furthermore, this will be possible through stable administrative and financial support from government and local agencies [21]. Hence, the result that the most significant number of respondents were distributed in Type 1 means the possibility of legal and institutional settlement of the "0th-period PE class".

Secondly, the Type 2 participants strongly believed that early morning exercise plays a significant role in leading to successful school life. Notably, respondents recognized that the program was helpful in social development, such as cooperation with others, interpersonal skills, and leadership building [39]. Moreover, unlike in regular classes, interaction with friends and teachers frequently occurs, leading to students' social development and expansion of social networks. These results mean that "0th-period PE class" helps students adapt to overall school life. Lee et al. [40] suggested that the program not only manages stress but also prevents deviations from school for students. Jeon et al. [20] explored Korean middle school students' subjective perception types and characteristics regarding participation in the "0th-period PE class". He concluded that the program was recognized as the driving force for students to maintain a stable school and could be an advantage of the morning exercise program from a parent's point of view.

Based on the discussion above, Type 2 was named "Beachhead for a vibrant school life: Implying interpersonal relationships, social skills, and adaptability". Meanwhile, participants in Type 2 recognized that "0th-period PE class" had a positive effect on school life but showed a negative perception of improving motor skills and physical fitness such as agility, muscular strength, and endurance.

Thirdly, Type 3 was named "Enhancement of academic capability: Increased concentration, positive learning attitude, and increased academic performance". In this type, positive perceptions of academic achievement were mainly derived. Interestingly, participants in Type 3 showed a negative perception about the development of social skills through the early morning exercise program.

Recently, scholars in kinesiology have shown scientific evidence of an association between physical activity and academic achievement. Research studies on a positive relationship between physical activity and academic achievement have been discussed [41–43], especially for those adolescent populations [4,6]. For example, Hobart [8] demonstrated that the morning exercise program improves the brain's structure and condition, improving academic performance. Furthermore, there is scientific evidence that physical activity can contribute to developing and activating the hippocampus, which has a significant role in learning and memory in the limbic system [44,45].

Studies conducted in Korea related to these topics produced similar results. For example, participation in the "0th-period PE class" improved high school students' academic performance than a control group that did not receive the morning exercise program [46]. However, the results also showed that students in the control group had more stress and mental issues. Park and Moon [16] mentioned that the morning exercise program could improve academic performance through increased concentration. Thus, the logical and theoretical connection between morning exercise and academic achievement supports the response of Type 3 participants.

Lastly, Type 4 is titled "Strengthening physical and mental health: Improving exercise function, increasing interest in PE classes, and leading a healthy daily life". Participants in this category were highly aware of the direct physical effects of participation in sports and exercise. Furthermore, experiencing the morning exercise program contributed to motivation and active participation in PE classes. Based on these results, the healthy daily life of student agency was logically derived. However, respondents of Type 4 showed a negative perception of the impact on academic performance through the early morning exercise program.

The benefits of early morning exercise have been substantially proven by scientific evidence in physiology and medical science [47]. For example, regular morning exercise program participation positively improved adolescents' motor skills, cardiorespiratory

endurance, and muscle strength [16,48]. Furthermore, the sports club activities in the "0thperiod PE class" significantly affected elementary school students' physical self-concept [49]. For this reason, the researchers draw attention to the fact that maintaining healthy daily life is possible by participating in "0th-period PE class" in terms of physical and mental benefits for adolescents [50,51]. Based on the above academic perspective, various perceptions of parents in the results of this study were discussed. A variety of previous studies have already published the effects of early morning exercise. However, this study has the ultimate goal of institutionalizing the "0th-period PE class" based on early morning exercise. Particularly, the positive perception of parents was derived in a different aspect from the students participating [20] in the "0th-period PE class". As remarked in the introduction, the role of parents is important in the institutional development of public education in South Korea. Thus, this study's findings can be an academic driving force for "0th-period PE class" to be operated as a regular class in the near future.
