Immense efforts have been implemented by the North Sumatera government since the beginning of the Covid-19 pandemic to mitigate the spread and the increasing numbers of cases. However, the numbers continued to grow, and Indonesia contributed to one of the highest numbers of Covid-19 among children globally. Although cases in children are commonly mild, but the long-term health impact of Covid-19 is still unknown. Therefore, protection against infection on the first place is highly important. We aimed to determine the prevalence of Covid-19 infection among high school students and their knowledge, attitude and practices (KAP) towards Covid-19 prevention. Methods: The study was conducted in Medan, Indonesia from 24 November 2020 to 12 January 2021. Nasopharyngeal swab specimen was collected from individuals. Detection of either E, N, and ORF1ab gene using RT-PCR was used to confirm the presence of current infection. The information on KAP was obtained from a self-administered questionnaire. Data on age, sex, district of residency, parents background, swab results were analyzed. Results: A total of 672 individuals were enrolled to the study. The majority of respondents had a good level of knowledge, attitudes, and practice against COVID-19, with percentage of 45.4%, 76.3%, 58.5% respectively. Conclusion: Most respondents have a good level of knowledge, attitudes, and practice against COVID-19