Cosmic rays are ubiquitous and readily available, making them a good teaching tool for particle and astrophysics by young students.
Tan-Q is an inclusive outreach and educational project, providing students in Japanese junior-high or high schools with research opportunities to join cosmic-ray and particle physics. In the Tan-Q framework, the students in each school conduct their research with help from mentors who are mainly undergraduate students. Researchers are also extensively involved through regular Zoom meetings and continuous communication on Slack. Some cases are inter-school, and some are international. This paper presents one of the Tan-Q activities of joint research between high schools in Japan and Argentina to observe cosmic-ray muons using Cosmic Watches. Our primary goal is to investigate the muon flux differences due to the differences in circumstances like altitudes and geomagnetic field strengths. Those involved learn not only particle physics but also statistical data analysis methods.