This study aims to determine the prevalence of symptomatic gastroesophageal reflux disease (GERD) in children aged 8-9 years and 12-13 years in the Czech Republic. Participants are recruited through schools and complete a web-based questionnaire assessing reflux-related symptoms. Children reporting pyrosis or regurgitation undergo a stepwise diagnostic evaluation that includes a standardized proton pump inhibitor (PPI) trial, upper endoscopy when indicated, and 24-hour pH-impedance monitoring for those with inconclusive findings. These procedures allow classification into confirmed GERD, reflux hypersensitivity, or functional pyrosis. All children undergoing diagnostic testing complete a validated quality-of-life questionnaire. The study will provide population-based prevalence estimates and evaluate symptom burden and potential risk factors associated with pediatric GERD.