Neurofeedback training has emerged as a promising non-pharmacological intervention for cognitive enhancement. This study investigates the effects of EEG-based neurofeedback training on attention, working memory, and executive function in healthy adolescents aged 15-18. We conducted a randomized controlled trial with 84 participants over 12 weeks, measuring cognitive performance through standardized assessments and neurophysiological markers via EEG recording. Results indicate significant improvements in sustained attention (p<0.001), working memory capacity (p<0.01), and cognitive flexibility (p<0.05) in the neurofeedback group compared to controls. The research provides evidence for accessible cognitive enhancement techniques applicable in educational settings.