It's not your imagination, classrooms are filled with children with auditory processing problems - for some it's mishearing, others have exquisite auditory sensitivity and become overwhelmed with normal school noise. Although clinicians have known for a long time that hearing loss and hearing hypersensitivity can occur in the same patients, the biological processes involved are just beginning to be understood.
Children often don't mention that they suffer from tinnitus (ringing in the ears), and there are no ways to detect it by a simple clinical test. The first link below shows how tinnitus can be 'seen' on functional brain imaging studies. When certain frequencies are lost in the brain, the 'hearing brain' reorganizes to try and compensate for the loss. The only problem is, the hearing of some frequencies may become overly sensitive, while the losses of others still persist. Interestingly, some of the most beneficial therapies for tinnitus are directed at introducing sound at the appropriate frequencies to allow the brain to reduce its self-generated sounds.
There are many reasons why we may be seeing more hearing loss, tinnitus, and sound hypersensitivities in school-aged children. Predisposing factors are many, but may include premature or stressful birth, frequent ear infections, and or autism spectrum disorders.
The diagnosis of brain-based auditory processing disorders is still in its infancy, although the pace of research and advancement in the areas of auditory training are exciting.
Seeing Tinnitus on fMRI
Tinnitus, Hyperacusis, and Hearing Loss
Hyperacusis in Autism
Auditory Processing and Language Difficulties in Prematurely Born