Children and youth of school age form a special population group highly sensitive to various stressors and negative effects in everyday life. The COVID-19 pandemic crisis characterized by uncertainty, vulnerability, changes in quality of life together with urgent transition to distant/online learning affected significantly psychological well-being of children and youth. The aim of this study was to assess the cross-cultural differences in actual stress in Russian and Kyrgyz schoolchildren with high and low levels of anxiety and depression during the initial stage of the COVID-19 pandemic and after a year life during the pandemic. The descriptive cross-sectional study was conducted via an online survey completed by total 1834 schoolchildren aged from 13 to 18 from Russia and Kyrgyzstan, the periods of survey: 10th May - 10th June, 2020; 18th May -15th June, 2021. The Perceived Stress Scale and Hospital Anxiety and Depression Scale were used to assess stress, anxiety and depression scores. The findings suggest that there are cross-cultural differences in perceived stress amongst schoolchildren with high level of depression and anxiety: Russian respondents in 2021 demonstrated less pronounced index of the perceived stress than Kyrgyz schoolchildren. The stress level of Kyrgyz schoolchildren increased significantly in 2021 in comparison to the period of outbreak of the pandemic. In 2021 in both countries we found the same pattern: girls had significantly more pronounced stress than boys. The results disclose important aspects of the impact of COVID-19 on schoolchildren and demonstrate the emerging need of psychological aid and for supporting schoolchildren mental health.