This study analyses opinions of primary school pupils and secondary school students (boys and girls) on physical education classes in Slovakia. The survey was conducted in 21 Slovak towns with 6959 respondents -- 3606 primary school pupils and 3353 secondary school students. Average age of boys from primary schools was 14.32 years ± 0.35 years and girls was 14.28 years ± 0.39 years. Average age of boys from secondary schools was 18.22 years ± 0.25 years and girls was 18.56 ± 0.38 years. It was carried out in school year 2018/2019. The survey was based on inquiry created and evaluated by Gamo Banska Bystrica's programme TAP3. The survey results were analysed in terms of sex and age differences (chi-square statistic). It was established that popularity of Physical education (PE) classes declines with age. Almost 50 % of boys and girls stated they are active during PE classes, however their activity declines with age, and therefore they become more passive. More than 50 % of pupils and students always or mostly feel good during PE, when the main activities of the classes are games and fun. The most popular activity in PE classes is playing sports games, with the survey response frequency of 58.91 %. The least popular are gymnastic exercises, with the survey response frequency of 44.49 %. The significant difference was noted among particular groups of respondents in terms of statistical significance (p < 0.01), especially from the point of view of the sex and age differences (primary school pupils vs. secondary school students).