It is often said that teaching children to play music has many benefits, including making them "smarter" and improving their school performance. Indeed, some literature exists to support such beliefs (see links below).
More recently, a study from Northwestern University sought to question whether playing a musical instrument can also impact age-related hearing loss and neuronal timing. The results of the study, which were published in the Journal Neurobiology of Aging, indicate that musicians had much improved neuronal timing and a greater ability to perceive sound than those who did not play an instrument. The study assessed this by taking both younger and older musicians and nonmusicians to compare these effects.
What is even more interesting is that according to Northwestern University's new center, the results of this study and those of animal models "strongly suggest that intensive training even late in life could improve speech processing in older adults and, as a result, improve their ability to communicate in complex, noisy acoustic environments". In other words, it is believed that nonmusicians can still pick up an instrument later in life and enjoy these benefits; albeit, not necessarily to the same degree.
Further enquiry into this phenomenon may very well show that learning music allows for the improved processing and/or neural timing, of other cognitive processes and therefore explain the observation that such students perform better in school than their nonmusician counterparts. Though this would certainly be much harder to assess due to the number of possible confounders (ie higher levels of discipline), it would certainly be rewarding if it were so, particularly if playing music could be incorporated as some form of rehabilitory mechanism after brain injury for example.