Chinese speech intelligibility was evaluated in 3 primary school classrooms with different reverberation time under the conditions with or without sound reinforcement system for children of different ages.The results show that，for both Grade 3 and Grade 5 children,when the interfered noise level in classrooms is relatively high (60dBA),not only the Chinese speech intelligibility scores without the sound reinforcement system but also the scores with the sound reinforcement system at a sound pressure level of 70 dBA are significantly improved and are higher than the scores with the sound reinforcement system at a sound pressure level of 75dBA.However,these in- telligibility scores are not significantly different from those obtained under the condition that the teacher uses normal speech sound pressure level to teach in quieter environmental noise conditions.It is thus concluded that,in order to obtain a speech intelligibility score equaling that without sound reinforcement system,a higher signal-to-noise ratio is needed when the sound reinforcement system is used.