Children are more impaired than adults by unfavorable listening conditions such as reverberation and noise. Nevertheless, the acoustical conditions in classrooms often do not fit the specific needs of young listeners. This field study aimed to analyze the effects of classroom reverberation on children's performance and well-being at school. Performance and questionnaire data were collected from 487 children from 21 classrooms which differed in mean reverberation time from 0.49 to 1.1 seconds. Significant effects of reverberation on speech perception and short-term memory of spoken items were found. Furthermore, the children from reverberating classrooms performed lower in a phonological processing task, reported a higher burden of indoor noise in the classrooms, and judged the relationships to their peers and teachers less positively than children from classrooms with good acoustics. The results demonstrate the importance of good acoustical conditions in classrooms. (Contains 2 tables and 5 figures.)