The paper presents the latest research concerning the correlation between changes in the school building room acoustics and noticeable changes in the communication, behaviour and wellbeing of students and teachers.The primary school covered by the research is the second largest school of this type in Poland. There was a comprehensive acoustic intervention in 2018 as a part of a pilot study for Warsaw municipality preparing for systematic improvement of acoustics in capital schools. This case gave an excellent opportunity to assess the impact of changes in room acoustics on pupils’ school performance, teachers’ effort and wellbeing of both groups.The research used the Acoustic Change Feelings Scale (SOZA) for teachers, parents and students, analysis of documentation and interviews. The questions concerned wide range of scholar activity aspects: concentration, speed of work, level of task fulfillment and school achievements, short term memory capacity, fatigue, pupils behaviour during lessons and breaks, level of excitement and aggression or teachers’ voice effort. Approximately 1,000 students, and 150 teachers were included in the study. Acoustic measurements were made (before and after acoustic treatment), including measurement of the equivalent sound level LAeq, reverberation time T, speech transmission index STI and spatial decay of sound.