Aim: The aim of the paper was to analyse nutrition disturbances, determine dietary habits and characterise physical activity among school children at the age of 6–13 in the Polish city of Piekary Śląskie. Material and methods: The study involved children aged 6–13 attending primary schools in Piekary Śląskie. There were 508 participants: 252 boys (49.61%) and 256 girls (50.39%). On the basis of the data collected, BMI was established and the level of nutrition was analysed. Additionally, dietary habits and the amount of physical activity were analysed statistically. Results: Obesity and overweight is present in nearly 38% of children. Simultaneously, every fifth child is malnourished. Slightly more than 45% of children have a proper number of meals per day. Approximately 67% of respondents have first and second breakfast every day. Only about 5% of pupils eat five or more portions of fruit or vegetables a day. Merely 53% of children consume milk and milk products regularly. Over 82% of pupils declare that they eat meat a few times a week. Nearly every third child eats sweets or salty snacks every day. About 60% of children prefer outdoor physical activity, and more than 21% systematically practise sport. Conclusions: The children examined – pupils attending primary schools – have improper dietary habits. They consume excess amounts of certain foods (mostly sweets), but too few vegetables and fruit, fish, milk and high-fibre grain products. Moreover, it was observed that physical activity in adolescence is inappropriate.