It is well documented that the interference of noise in the classroom puts younger pupils at a disadvantage for speech perception tasks. Nevertheless, the dependence of this phenomenon on the type of noise, and the way it is realized for each class by a specific combination of intelligibility and effort have not been fully investigated. Following on a previous laboratory study on "listening efficiency," which stems from a combination of accuracy and latency measures, this work tackles the problems above to better understand the basic mechanisms governing the speech perception performance of pupils in noisy classrooms. Listening tests were conducted in real classrooms for a relevant number of students, and tests in quiet were also developed. The statistical analysis is based on stochastic ordering and is able to clarify the behavior of the classes and the different impacts of noises on performance. It is found that the joint babble and activity noise has the worst effect on performance whereas tapping and external traffic noises are less disruptive.